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Evaluation of the potential for virus dispersal during hand drying: A comparison of three methods

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Aims: To use a MS2 bacteriophage model to compare three hand-drying methods, paper towels (PT), a warm air dryer (WAD) and a jet air dryer (JAD), for their potential to disperse viruses and contaminate the immediate environment during use. Methods and results: Participants washed their gloved hands with a suspension of MS2 bacteriophage and hands were dried with one of the three hand-drying devices. The quantity of MS2 present in the areas around each device was determined using a plaque assay. Samples were collected from plates containing the indicator strain, placed at varying heights and distances and also from the air. Over a height range of 0.15-1.65 m, the JAD dispersed an average of >60 and >1300-fold more plaque-forming units (pfu) compared to the WAD and PT (P <0.0001), respectively. The JAD dispersed an average of >20 and >190-fold more pfu in total compared to WAD and PT at all distances tested up to 3 m (P <0.01), respectively. Air samples collected around each device 15 minutes after use indicated that the JAD dispersed an average of >50 and >100-fold more pfu compared to the WAD and PT (P <0.001), respectively. Conclusions: Use of the JAD lead to significantly greater and further dispersal of MS2 bacteriophage from artificially contaminated hands when compared to the WAD and PT. Significance and impact of study: The choice of hand drying device should be considered carefully in areas where infection prevention concerns are paramount, such as healthcare settings and the food industry. This article is protected by copyright. All rights reserved.
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ORIGINAL ARTICLE
Evaluation of the potential for virus dispersal during hand
drying: a comparison of three methods
P.T. Kimmitt and K.F. Redway
Department of Biomedical Sciences, Faculty of Science and Technology, University of Westminster, London, UK
Keywords
aerosolization, cross-contamination, dispersal,
hand drying, hand hygiene, MS2
bacteriophage, virus.
Correspondence
Patrick T. Kimmitt, Department of Biomedical
Sciences, Faculty of Science and Technology,
University of Westminster, 115 New Cavend-
ish Street, London W1W 6UW, UK.
E-mail: p.kimmitt@westminster.ac.uk
2016/1655: received 18 August 2015, revised
12 November 2015 and accepted 22 Novem-
ber 2015
doi:10.1111/jam.13014
Abstract
Aims: To use a MS2 bacteriophage model to compare three hand-drying
methods, paper towels (PT), a warm air dryer (WAD) and a jet air dryer
(JAD), for their potential to disperse viruses and contaminate the immediate
environment during use.
Methods and Results: Participants washed their gloved hands with a
suspension of MS2 bacteriophage and hands were dried with one of the three
hand-drying devices. The quantity of MS2 present in the areas around each
device was determined using a plaque assay. Samples were collected from
plates containing the indicator strain, placed at varying heights and distances
and also from the air. Over a height range of 015165 m, the JAD dispersed
an average of >60 and >1300-fold more plaque-forming units (PFU) compared
to the WAD and PT (P<00001), respectively. The JAD dispersed an average
of >20 and >190-fold more PFU in total compared to WAD and PT at all
distances tested up to 3 m (P<001) respectively. Air samples collected
around each device 15 min after use indicated that the JAD dispersed an
average of >50 and >100-fold more PFU compared to the WAD and PT
(P<0001), respectively.
Conclusions: Use of the JAD lead to significantly greater and further dispersal
of MS2 bacteriophage from artificially contaminated hands when compared to
the WAD and PT.
Significance and Impact of Study: The choice of hand-drying device should be
considered carefully in areas where infection prevention concerns are
paramount, such as healthcare settings and the food industry.
Introduction
The importance of hand hygiene in minimizing the risk
of transmission of pathogenic micro-organisms has been
recognized since Semmelweis’s work on puerperal fever
transmission (Codell Carter 1983). Hand hygiene is con-
sidered to be an integral component of the practice of
infection control both in the home and in community
and healthcare settings (Curtis et al. 2003; Bloomfield
et al. 2007). It has been estimated that cross-infection
contributes to 40% of cases of healthcare-associated
infections and hand hygiene compliance represents an
essential step in minimizing such infections (Pittet 2000;
Weist et al. 2002; Pittet et al. 2006). Hand hygiene
comprises two different possible procedures; decontami-
nation using a hand sanitizer, such as alcohol, or washing
with soap and water and, with the latter, drying of the
hands by various methods.
In healthcare settings, the appropriate cleansing of the
hands of staff or visitors prior to, or after, certain proce-
dures is of particular importance and various guidelines
on hand washing and cleansing have been issued by the
CDC (Centers for Disease Control and Prevention 2002),
the NHS (National Health Service) and the WHO (World
Health Organization) (Boyce and Pittet 2002; WHO 2009;
NHS Professionals 2013). The WHO guidelines state that
water alone is unsuitable for cleaning visibly soiled hands
and that soap or detergent must be used as well as water.
Journal of Applied Microbiology 120, 478--486 ©2015 The Society for Applied Microbiology478
Journal of Applied Microbiology ISSN 1364-5072
There has been much research on the effectiveness of
soap and other agents in reducing the microbial count of
both resident and transient flora on the hands. A study
and review of the literature concluded that the main fac-
tors affecting bacterial counts on the hands were the
hand sanitizer or soap used and the drying method
(Montville et al. 2002) and that hands which are inade-
quately dried are more likely to transmit micro-organ-
isms when compared to those which have been
completely dried (Patrick et al. 1997).
The importance of thorough cleansing of the hands
with soap and water or a hand sanitizer to reduce health-
care-associated infections is well documented, having
been publicized for years such as by National Health Ser-
vice poster campaigns and by initiatives such as the
Cleanyourhands campaign (Stone et al. 2012). However,
in reality the general public and some healthcare profes-
sionals do not always follow the advice. Washing proce-
dures can be poor and compliance rates low (Knights
et al. Unpublished data; Anderson et al. 2008).
If it is accepted that the hands become contaminated
with micro-organisms when using the toilet, these studies
would indicate that, due to low compliance rates and
inadequate hand cleansing procedures, the majority of
persons drying their hands in washrooms are likely to
have microbial contamination on their hands when they
dry them. This has implications for the aerosolization
and dispersal of that contamination by the hand-drying
method that is used and the risk of transmission of
potentially disease-causing micro-organisms into the
washroom environment and to other persons using the
washroom.
There are a number of different methods available for
hand drying in public washrooms. These include paper
towels, continuous roller towels, warm air dryers and jet
air dryers. There have been relatively few studies evaluat-
ing the capacity for the different hand-drying devices to
aerosolize and disperse microbial contamination on the
hands into the immediate environment and to other per-
sons using a washroom. Matthews and Newsom (1987)
concluded that there was no significant difference
between warm air dryers and paper towels in terms of
aerosol liberation and that the former could be consid-
ered safe but Ngeow et al. (1989) demonstrated the dis-
persal of marker bacteria within a radius of 1 m from a
warm air dryer. When comparing the use of paper towels
with a jet air dryer to dry the hands of 100 volunteers,
Margas et al. (2013) showed that the two hand-drying
methods produced different patterns of ballistic droplets:
the jet air dryer producing a greater number of droplets
dispersed over a larger area and more microbial contami-
nation of the immediate environment than paper towels.
Best et al. (2014) used a paint and a Lactobacillus bacte-
rial model to compare aerosolization and dispersal fol-
lowing hand drying with paper towels, a warm air or jet
air dryer. They showed that paper towels produced less
dispersal from the hands into the surrounding environ-
ment than jet air dryers. Using an acid-indicator model
and artificial contamination of the hands with yeast, Best
and Redway (2015) demonstrated that the use of a jet air
dryer to dry the hands dispersed liquid, and, conse-
quently, potential microbial contamination on the hands,
to greater distances (up to 15 m) than paper towels,
roller towels or warm air dryers (up to 075 m). In the
same study, jet air dryers were also shown to disperse
more liquid from the hands to a range of different
heights compared to the other hand-drying methods.
However, such studies have focused on micro-organisms
other than viruses and to date there have been few stud-
ies to evaluate the aerosolization and dispersal of virus
particles during hand drying.
Viral pathogens such as Norovirus are thought to have
a low infectious dose and can be shed in large numbers
in faeces (Gerhardts et al. 2012). In a review, Kampf and
Kramer (2004) cited studies that show that viruses can
survive on the hands for varying times; Influenza and
CMV (1015 min), HSV (up to 2 h), Adenovirus (for
many hours), Rhinovirus (7 days) and Rotavirus and
HAV (up to 60 days). Therefore, virus dispersal in the
washroom has the potential to contaminate persons and
surfaces, including those of hand-drying devices.
This study used bacteriophage MS2 as a surrogate for
nonenveloped human viruses. MS2 has been used in this
way in a number of prior studies due to its stability and
similar characteristics to human enteric viruses such as
Picornaviruses and Caliciviruses, including Norovirus
(Sickbert-Bennett et al. 2005; Gerhardts et al. 2012).
Additionally, MS2 has the added advantage in that virus
numbers can be readily quantified using a plaque assay.
In this work, the capacity for three hand-drying devices,
namely paper towels, a warm air dryer and a jet air dryer,
to aerosolize and disperse water on the hands, and con-
taminate the air and surfaces around the drying device
with MS2 phage was investigated.
Materials and methods
Preparation and use of MS2 bacteriophage
MS2 bacteriophage (ATCC 15597-B1) was propagated at
37°C overnight in log phase tryptone soya broth (Oxoid,
Basingstoke, UK) cultures of Escherichia coli (ATCC
15597) to yield a mean count in the range of 10
10
pla-
que-forming units (PFU) per mL. Following infection,
nonlysed bacteria were removed by centrifugation
(3000 g, 10 min) and the supernatant phage suspension
Journal of Applied Microbiology 120, 478--486 ©2015 The Society for Applied Microbiology 479
P.T. Kimmitt and K.F. Redway Virus dispersal during hand drying
generated was used in subsequent experiments. Each
batch of phage suspension was titrated on the same day
as experiments were performed to ensure that approxi-
mately equal numbers of phage particles were used each
time. Participants were asked to rinse their gloved hands
in 50 ml of the phage suspension for 10 s and simulate
the process of washing during this period followed by
shaking three times and then drying them using one of
the hand-drying devices. All experimental work took
place in a university teaching laboratory and the washing
and drying areas were separated by a distance of approx.
5m.
For quantitative detection of MS2 phage, plates of
tryptone soya agar (TSA) (Oxoid) were overlaid with a
thin layer of 05% sloppy TSA containing 1% (v/v) log
phase Escherichia coli (ATCC 15597). Dispersal experi-
ments were performed and, following incubation over-
night at 37°C, the number of plaque-forming units
determined by visualization and counting of plaques.
Hand-drying devices
Three hand-drying methods were compared in this study;
the use of two paper towels (Wepa Clou Comfort, Arns-
berg, Germany) for 10 s, warm air drying (World Dryer
Corporation, Berkeley, IL), model LE48 for 20 s and jet
air drying (Dyson, Malemsbury, UK), model AB01 for
10 s. Drying times for the paper towel and warm air
dryer were based on the mean times recorded during the
observation of 292 members of the public in male and
female washrooms in various London locations (Knights
et al. Unpublished data). The 10-s drying time for the jet
air dryer was based on the manufacturer’s recommenda-
tions displayed on the device. The devices were mounted
onto a wooden board placed at a height that would be
typical for use in a washroom. The dryers used were not
new but had never been used in a washroom and were
decontaminated between tests by thorough wiping with
70% (v/v) ethanol.
Virus dispersal at different heights and distances
90 mm diameter Petri dishes (Fisher Scientific, Lough-
borough, UK) containing TSA and an overlay of the
E. coli host were affixed to a vertical board at intervals of
030 m at six different heights (015, 045, 075, 105,
135 and 165 m) from the floor. The agar plates were
affixed to the mid-point of six zones (16) chosen to
represent a typical human torso, including head, trunk
and legs, of a person using a washroom (Fig. 1). During
tests, the vertical board was held 04 m from the hand-
drying device; this distance being based on measurement
of the mean distance between multiple hand-drying
devices in large public washrooms at a mainline railway
station.
Air sampling
An Air Trace
â
Environmental air sampler (Biotrace, Run-
corn, UK) model ATEM 240 with a 1 m Tygon tube was
used to sample air in the vicinity of each hand-drying
device at a rate of 283 l min
1
, a total of 4245 l of air
was sampled. The air was impacted at 70 m s
1
via a
44 90152 mm slit onto a rotating 140 mm Petri dish
(Fisher Scientific) containing 05% sloppy TSA with 1%
(v/v) log phase Escherichia coli (ATCC 15597).
Petri dishes were orientated so that the start point
could be determined and sampling was performed over a
period of 15 min, after which the plate had made one
complete rotation. The air sampler was subjected to a 1-h
purge cycle before and after daily use and in between
changes of hand-drying device. In addition, a 15-min
control air sample was collected before each run or
change of hand-drying device. As with the height and
distance dispersal experiments, settle plates were placed
around each device to confirm that no residual MS2
phage was present at the beginning and end of each test
run.
In order to assess virus dispersal in air a method based
on that used by Best et al. (2014) was employed. The
Tygon tube inlet was placed at a height of 12 m which
corresponded to the height of both the bottom of the
paper towel dispenser and the bottom of the warm air
dryer and was 025 m above the height of the jet air
dryer.
(1·65 m)
(1·35 m)
(1·05 m)
(0·75 m)
(0·45 m)
(0·15 m)
ZONE 1
ZONE 2
ZONE 3
ZONE 4
ZONE 5
ZONE 6
Figure 1 Photograph of vertical board with human figures and dia-
gram showing the 6 different height zones and height of mid-point
from floor (m) used to assess vertical dispersal.
Journal of Applied Microbiology 120, 478--486 ©2015 The Society for Applied Microbiology480
Virus dispersal during hand drying P.T. Kimmitt and K.F. Redway
Air samples were collected at three different positions
(Fig. 2):
i At a distance of 01 m from the left and right-hand
side of each device;
ii At a distance of 1 m from the left and right-hand side
of each device;
iii At a 1 m distance behind and offset by 03 m from
the right-hand side of the device.
Two participants were used and an equal number (10)
of samples were taken from the left and right-hand side
for each of the distances and positions used. The
sequence by which different samples were collected and
devices tested was randomised.
After incubation, plates were divided into six sectors,
each sector representing a 25-min time interval and the
number of PFU in each sector was counted. Where pla-
que formation was confluent, semi-confluent or uncount-
able, and for calculation purposes, the number of plaques
per sector was recorded as follows: confluent plaque for-
mation was scored as 500 per sector; confluent/semi-con-
fluent plaque formation was scored as 400 per sector;
semi-confluent plaque formation was scored as 300 per
sector; uncountable numbers of plaque were scored as
200 per sector. Uncountable refers to the presence of dis-
crete plaques that were present in high numbers which
could not be counted with accuracy.
When necessary to enable visualization of plaques as
clear areas against a red background, the plates were
flooded with tryptone soya broth (Oxoid) containing
01% (w/v) 2,3,5, triphenyltetrazolium chloride (Fisher
Scientific) followed by incubation at 37°C for 20 min
(Pattee 1966).
Statistical analysis
Data from plaque assays were analysed by Students t-test
using MICROSOFT EXCEL (Microsoft, Redmond, WA), with a
confidence interval of 95%. A Pvalue of <005 was used
to denote statistical significance.
Results
Virus dispersal at different heights
The vertical board with attached Petri dishes was divided
into six zones to compare virus dispersal at a range of
heights covering a range of 015165 m (Fig. 1). For
each of the six zones, a total of at least ten replicates were
used for each hand-drying device performed approxi-
mately equally on the left and right-hand side of the
device.
The jet air dryer dispersed a significantly greater num-
ber of virus particles than the other hand-drying devices
(Table 1). The greatest mean number of PFU was
observed in zones 3 (075 m) and 4 (105 m), 710 and
834 PFU respectively. These two zones represented nearly
70% of the total detected virus dispersed by the jet air
dryer. In contrast, the warm air dryer dispersed a mean
of 5 PFU in zone 4, 167-fold lower than the jet air dryer
and with the difference being significant (P<00001).
Paper towels dispersed a mean of 01 PFU in zone 4,
8340-fold lower than the jet air dryer (P<00001). Con-
trol samples collected with the devices switched off and
0·3 m<<>>0·7 m
1
3
2
DEVICE
Figure 2 Diagram showing the three different air sampling positions
used in this study.
Table 1 Counts of viral plaques on 90 mm agar plates of a bacterial
lawn at different heights at a set distance (04 m) from hand-drying
devices used to dry the hands of participants after contamination
with a bacteriophage suspension. Data are presented as means with
standard deviation in parentheses
Height zone
Height
from
floor (m)
Mean number of plaques (SD)
Paper
towel
Warm air
dryer Jet air dryer
1165 05(10) 07(17) 2489 (3096)
2135 07(16) 87 (107) 3359 (2850)
3105 01(03) 46(49) 7095 (3319)
4075 01(03) 54(65) 8336 (2583)
5045 01(03) 39(45) 639 (897)
6015 01(03) 111 (146) 269 (444)
N111111
Mean
total number
(all heights)
16344 22187
Journal of Applied Microbiology 120, 478--486 ©2015 The Society for Applied Microbiology 481
P.T. Kimmitt and K.F. Redway Virus dispersal during hand drying
performed before and after each experiment yielded no
plaques.
Virus dispersal at different distances
Comparisons of virus dispersal at varying distances from
the hand-drying device were performed using Petri dishes
placed on a vertical surface at 02505 m intervals and
ten replicates were assayed for each distance point, per-
formed equally on the left and right-hand side of the
device. Distances from 0 to 3 m were compared and at
all distances tested the jet air dryer dispersed significantly
greater (P<001) numbers of virus particles than either
the warm air dryer or paper towel devices (Table 2). For
the jet air dryer, the maximum mean number of PFU
was seen 025 m from the device and there was a decline
in PFU with increasing distance from the device. How-
ever, the mean number of PFU observed 3 m from the
device was more than 500-fold greater than that for the
warm air dryer and paper towel devices (Fig. 3). Control
samples collected with the device switched off and per-
formed before and after each experiment yielded no pla-
ques.
Air sampling
For all three devices, PFU counts were generally greater
when air samples were collected closer to the device, in
this case 01 m compared to 1 m (Table 3) and the num-
ber of detectable PFU decreased over time (Fig. 4). How-
ever, airborne virus counts for the jet air dryer were
significantly greater (P<0001) than those for the warm
air dryer and paper towel devices for each position and
for each time interval.
For the jet air dryer, during the immediate 25 min
after use and at 01 m from the device, 30-fold and 13-
fold more PFU were detected in air compared to the
warm air dryer and paper towel devices respectively (be-
tween which there was no significant difference). For the
last time period (12515 min) after hand drying, more
than 50-fold numbers of PFU were detected when the jet
air dryer was tested at any of the three sample positions
used compared to paper towels and the warm air dryer.
The number of PFU detected in the air from the jet air
Table 2 Counts of viral plaques on 90 mm agar plates of a bacterial
lawn at a set height (071 m) and at different distances from hand-
drying devices used to dry the hands of participants after contamina-
tion with a bacteriophage suspension. Data are presented as means
with standard deviation in parentheses
Distance
from device (m)
Mean number of plaques (SD)
Paper towel Warm air dryer Jet air dryer
000 132(84) 502 (261) 5655 (4271)
025 00(00) 490 (313) 9240 (1946)
050 00(00) 38(23) 5468 (4285)
075 00(00) 11(14) 3221 (3194)
100 20(28) 02(04) 2123 (2245)
150 02(04) 02(04) 2143 (1908)
200 00(00) 00(00) 1845 (2150)
250 00(00) 00(00) 1799 (2051)
300 00(00) 03(06) 1774 (2435)
N101020
Mean
total number
(all distances)
154 1037 30045
1000·0
800·0
600·0
400·0
Mean number of plaques per plate
200·0
0·0
0·00 0·50 1·00 1·50
Distance (m)
2·00 2·50 3·00
Figure 3 Mean number of viral plaques per
90 mm bacterial overlay agar plate detected
at different distances after use of three hand-
drying devices: jet air dryer (); warm air
dryer (); paper towel (). Standard error
bars are shown.
Journal of Applied Microbiology 120, 478--486 ©2015 The Society for Applied Microbiology482
Virus dispersal during hand drying P.T. Kimmitt and K.F. Redway
dryer showed exponential decline with an acceptable
coefficient of determination (R²)of09781.
When drying hands using paper towels, virus counts in
the air to the sides of the device were slightly higher than
those obtained using a warm air dryer for most of the
time periods but this difference was not statistically sig-
nificant. Additionally, sampling at 1 m offset by 03m
behind the device produced no statistical difference
between paper towels and warm air drying. Control sam-
ples run before and after each experiment yielded no pla-
ques and no differences could be detected between
sampling on the left or right-hand side of any of the
hand-drying devices.
Discussion
When the three hand-drying devices were compared in
this study, there were clear differences in the extent of
virus dispersal from the hands. This was evident from the
results of the experiments in which MS2 was dispersed
from the hands and transferred onto agar plates affixed
at varying heights and distances from the hand-drying
devices and also into the air as sampled at three different
positions in the vicinity of the device. In each case, the
jet air dryer produced significantly greater virus dispersal
compared to the warm air dryer and paper towel devices.
Combined results for all six heights tested showed that
Table 3 Counts of viral plaques produced by air sampling at three different positions onto 140 mm agar plates of a bacterial lawn at different
times over a 15-min period after use of hand-drying devices to dry the hands of participants subsequent to contamination with a bacteriophage
suspension
Time (min) Distance (m) Position
Mean number of plaques (SD)
Paper towel Warm air dryer Jet air dryer
002501L&R367 (245) 159 (126) 4700 (458)
10L&R178 (215) 92 (100) 3500 (1025)
10/03B 69(88) 91(82) 3430 (790)
Mean total (L, R & B) 205 (231) 114 (109) 3877 (978)
Max/Min 790/00350/00 5000/2000
25500152(38) 44(3
5) 2357 (500)
1068(65) 52(75) 2000(00)
10/0337(38) 73(86) 2300 (458)
Mean total (L, R & B) 52(51) 56(70) 2267 (428)
Max/Min 190/00270/00 3000/2000
50750142(45) 22(26) 1798 (610)
1023(40) 19(25) 1345 (615)
10/0327(29) 55(52) 1220 (604)
Mean total (L, R & B) 31(39) 32(40) 1454 (661)
Max/Min 130/00160/00 3000/180
751000118(19) 27(22) 1012 (471)
1019(28) 10(09) 858 (661)
10/0324(30) 12(15) 703 (634)
Mean total (L, R & B) 20(26) 16(18) 858 (617)
Max/Min 90/0050/00 2000/40
1001250111(27) 18(25) 572 (542)
1009(16) 08(15) 465 (360)
10/0304(09) 19(23) 439 (458)
Mean total (L, R & B) 08 (231) 15(22) 492 (471)
Max/Min 90/0080/00 2000/20
1251500100(00) 14(21) 610 (482)
1010(20) 05(12) 385 (318)
10/0301(03) 06(12) 318 (380)
Mean total (L, R & B) 04(13) 08(16) 438 (425)
Max/Min 60/0060/00 1860/00
Data are presented as means with standard deviation in parentheses. L, left-hand side of device; R, right-hand side of device; B, 1 m behind
device with 03 m offset; Max, maximum plaque count; Min, minimum plaque count; N, 30 (5 for each position and time period).
Confluent plaque formation was scored as 500 per sector.
Confluent/semi-confluent plaque formation was scored as 400 per sector.
Semi-confluent plaques formation was scored as 300 per sector.
Uncountable plaque formation was scored as 200 per sector.
Journal of Applied Microbiology 120, 478--486 ©2015 The Society for Applied Microbiology 483
P.T. Kimmitt and K.F. Redway Virus dispersal during hand drying
the jet air dryer produced over 60 times more viral pla-
ques than the warm air dryer, and over 1300 times more
than paper towels (P<00001). The maximum numbers
of plaques detected were at a height range of 075
125 m which would equate to the height of the face of a
small child standing near the device when operated by
their parent. Virus dispersal was detected up to 3 m from
the jet air dryer. Combined results for all nine distances
tested showed that the jet air dryer produced over 20
times more viral plaques than the warm air dryer, and
over 190 times more than paper towels (P<001). Com-
bined results for the air counts after 15 min at the three
sampling positions showed that the jet air dryer produced
over 50 times more viral plaques than the warm air
dryer, and over 100 times more than paper towels
(P<0001). The number of PFU detected in the air
showed exponential decline which would suggest that
virus would still be present in the air beyond the 15-min
period used in this study.
These differences in results between the three hand-
drying devices can be largely explained by their mode of
drying the hands: paper towels remove water by absorp-
tion; warm air dryers of the type tested remove water
mainly by evaporation (Huang et al. 2012); jet air dryers
remove water by shearing forces and dispersal into the air
(Snelling et al. 2010). Furthermore, the use of paper tow-
els produces relatively little air movement and, while warm
air dryers produce more, the air movement is mainly
downwards. In contrast, jet air dryers generate air speeds
which are claimed to be over 600 kph and the movement
of air out of the chamber of the device is sideways.
This study used a standardized method of hand drying
and so did not take into account the variations in indi-
vidual behaviour, or the behaviour of participants outside
of the laboratory. Both participants were of a similar height
and the effect of a user’s physical dimensions on virus dis-
persal, particularly the distribution of plaques onto differ-
ent height zones (Fig. 1) was not addressed. Gloved hands
were artificially contaminated with a relatively high con-
centration of MS2 but the inoculum was standardized for
all three hand-drying methods. When counting plaques,
for plate sectors that were confluent, confluent/semi-
confluent or semi-confluent or over 200 (the limit of the
counting method) it is likely that the numbers of PFU
assigned to such plate sectors (500, 400, 300 and 200
respectively) underestimated the true numbers of plaques
present. Finally, it is acknowledged that only one example
of each type of hand-drying device was tested.
A high bacteriophage concentration of ~10
10
PFU ml
1
was used in this study but work on the shedding of Rota-
virus and Norovirus indicate that similar levels, or greater,
can be present in faeces during gastro-intestinal infections
(Ward et al. 1984; Atmar et al. 2008) and, therefore, also
on contaminated hands which have not been washed, or
washed inadequately. Although a bacteriophage model was
used to demonstrate aerosolization and dispersal by three
hand-drying methods, the implications for the transmis-
sion of actual viral pathogens in washrooms are clear. The
jet air dryer produced significantly greater dispersal at dif-
ferent heights and different distances than the warm air
dryer or paper towels. The jet air dryer also produced sig-
nificantly greater aerosolization of virus on the hands than
the other two hand-drying methods, with virus being
detected 15 min after use. The results of this study suggest
that in locations where hygiene and cross-infection consid-
erations are paramount, such as healthcare settings and
the food industry, the choice of hand-drying method
should be considered carefully.
450·0
400·0
350·0
250·0
150·0
200·0
300·0
Mean number of plaques per plate
100·0
0·0
50·0
0·0–2·5 5·0–7·5 10·0–12·52·5–5·0 7·5–10·0 12·5–15·0
Time interval (min)
Figure 4 Graph of mean number of viral
plaques per 140 mm bacterial overlay agar
plate detected by air sampling over 15 min at
25-min time intervals after use of three
hand-drying devices: jet air dryer (); warm
air dryer (); paper towel (). Standard error
bars and exponential trendline ( ) are
shown.
Journal of Applied Microbiology 120, 478--486 ©2015 The Society for Applied Microbiology484
Virus dispersal during hand drying P.T. Kimmitt and K.F. Redway
Conflict of Interest
This study was independently funded in full from a
University of Westminster research reserve account. Keith
Redway has received honoraria from the European Tissue
Symposium for microbiological advice and travel
expenses to attend meetings and conferences.
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Journal of Applied Microbiology 120, 478--486 ©2015 The Society for Applied Microbiology486
Virus dispersal during hand drying P.T. Kimmitt and K.F. Redway
... A number of studies have shown comparable concentrations of bacteria in air for jet air dryers and paper towels (16,18). Other studies have shown higher dispersal of bacteria and virus in the air when using electric dryers (19,20), but in some cases their experimental methodologies employed gloved and unwashed hands, which were not representative of real world conditions (17). Furthermore, there is a lack of experimental studies that quantify the distribution of smaller aerosols (< 10 µm), which may remain suspended in air for long periods (minutes to hours), generated by different hand drying methods. ...
... Figures 1C,D shows air samplers placed at three different locations in relation to the hand dryer, with particle counters placed at location 1, 2, and 3 to quantify aerosol number concentrations and bio-samplers placed at locations 1' , 2, and 3 to quantify bacteria in air as total viable counts. The samplers were placed 1.5 m above the floor to represent the adult breathing zone (20). The air of the chamber was purged before the start of the experiment and pre-test (background) samples obtained to quantify aerosols and bacteria counts. ...
... The non-statistically significant impact of jet air dryers on bacterial load in air is consistent with results from other studies, which also obtained comparable numbers when hands were dried with jet air dryers or paper towels (16,18). Other authors have reported that drying hands with jet air dryers resulted in much higher level of virus and bacteria concentrations in air (19,20), however these experiments employed unrealistic experimental conditions (17,21). ...
Article
Full-text available
Effective hand drying is an important part of hand hygiene that can reduce the risk of infectious disease transmission through cross-contamination of surfaces by wet hands. However, hand drying methods may also cause aerosolisation of pathogenic microorganisms if they are present in washed hands. This study investigated experimentally the impact of washing hands and different hand drying methods on the concentration and size distribution of aerosols and bacteria in indoor air. In this experiment, aerosol and bacteria concentrations were measured in indoor air while volunteers rinsed their hands with water or washed with soap and water prior to drying them with paper towels or jet air dryers. Results showed that the concentration of aerosols and bacteria in air increased with people walking in the room and washing hands, with a further increase during the hand drying process. The concentration of aerosols decreased with particle size, with maximum concentrations after drying hands of 6.63 × 10 ⁶ ± 6.49 × 10 ⁵ and 2.28 × 10 ⁴ ± 9.72 × 10 ³ particles m ⁻³ for sizes 0.3 to <0.5 and ≥5.0 μm, respectively. The concentration of bacteria in indoor air after drying hands increased to a maximum of 3.81 × 10 ² ± 1.48 × 10 ² CFU m ⁻³ (jet air dryers) and 4.50 × 10 ² ± 4.35 × 10 ¹ CFU m ⁻³ (paper towels). This study indicates that the increase of aerosols and bacteria in air after drying hands with jet air dryers or paper towels are comparable and not statistically different from concentrations associated with walking and washing hands in the same environment. This work can support the development of hand hygiene practices and guidelines for public washrooms.
... A number of studies were conducted in laboratories simulating unrealistic washroom conditions, including drying of unwashed or gloved hands covered with model organism solutions (Best et al., 2014;Best and Redway, 2015). Eleven studies were assessed as good quality (Aithinne et al., 2019;Boone and Gerba, 2005;Inkinen et al., 2017;Knowlton et al., 2018;Margas et al., 2013;Mkrtchyan et al., 2013;Mohamed et al., 2015;Snelling et al., 2011;Suen et al., 2019;Verani et al., 2014;Zapka et al., 2011), 16 studies were assessed as fair quality (Boxman et al., 2009a;Breathnach et al., 2012;Carducci et al., 2016;Cooper et al., 2016;Flores et al., 2011;Gormley et al., 2017;Halabi et al., 2001;Harrison et al., 2003;Kanayama Katsuse et al., 2017;Katano et al., 2014;Kurgat et al., 2019;Patrick et al., 2010;Pitt et al., 2018;Sassi et al., 2018;Taylor et al., 2000;Tsunoda et al., 2019), and the remaining 11 studies were assessed as poor quality (Alharbi et al., 2016;Best et al., 2018;Best et al., 2014;Best and Redway, 2015;Best et al., 2012;Boxman et al., 2009a;Gerhardts et al., 2012;Huesca-Espitia et al., 2018;Kimmitt and Redway, 2016;Kouadri, 2020;Repp et al., 2013). ...
... The main reasons for poor quality classification included poor or limited description of methods (Alharbi et al., 2016;Boxman et al., 2009a;Kouadri, 2020), sub-optimal sampling methods (Alharbi et al., 2016;Huesca-Espitia et al., 2018;Kouadri, 2020); lack of significance testing (Best et al., 2012); over-interpretation of limited experimental results (Best et al., 2018;Best et al., 2014;Best and Redway, 2015); and unrealistic experimental conditions, such as results based on gloved hands (Best et al., 2014;Best and Redway, 2015;Kimmitt and Redway, 2016) which could affect the interaction between resident and transient bacteria, washing procedure and drying time. ...
... Sixteen studies identified droplets as the potential route of transmission for infectious diseases associated with bacteria (Alharbi et al., 2016;Best et al., 2018;Best et al., 2014;Best and Redway, 2015;Best et al., 2012;Carducci et al., 2016;Cooper et al., 2016;Gormley et al., 2017;Kanayama Katsuse et al., 2017;Katano et al., 2014;Kimmitt and Redway, 2016;Knowlton et al., 2018;Margas et al., 2013;Sassi et al., 2018;Taylor et al., 2000;Verani et al., 2014). Details of microbial species First flush: reduced by~3 logs After 3 flushes: reduced bỹ 4-5 logs Floor: usually 1 or 2 CFU (max 4 CFU). ...
Article
Full-text available
Background The risk of infectious disease transmission in public washrooms causes concern particularly in the context of the COVID-19 pandemic. This systematic review aims to assess the risk of transmission of viral or bacterial infections through inhalation, surface contact, and faecal-oral routes in public washrooms in healthcare and non-healthcare environments. Methods We systematically reviewed environmental sampling, laboratory, and epidemiological studies on viral and bacterial infection transmission in washrooms using PubMed and Scopus. The review focused on indoor, publicly accessible washrooms. Results Thirty-eight studies from 13 countries were identified, including 14 studies carried out in healthcare settings, 10 in laboratories or experimental chambers, and 14 studies in restaurants, workplaces, commercial and academic environments. Thirty-three studies involved surface sampling, 15 air sampling, 8 water sampling, and 5 studies were risk assessments or outbreak investigations. Infectious disease transmission was studied in relation with: (a) toilets with flushing mechanisms; (b) hand drying systems; and (c) water taps, sinks and drains. A wide range of enteric, skin and soil bacteria and enteric and respiratory viruses were identified in public washrooms, potentially posing a risk of infection transmission. Studies on COVID-19 transmission only examined washroom contamination in healthcare settings. Conclusion Open-lid toilet flushing, ineffective handwashing or hand drying, substandard or infrequent surface cleaning, blocked drains, and uncovered rubbish bins can result in widespread bacterial and/or viral contamination in washrooms. However, only a few cases of infectious diseases mostly related to faecal-oral transmission originating from washrooms in restaurants were reported. Although there is a risk of microbial aerosolisation from toilet flushing and the use of hand drying systems, we found no evidence of airborne transmission of enteric or respiratory pathogens, including COVID-19, in public washrooms. Appropriate hand hygiene, surface cleaning and disinfection, and washroom maintenance and ventilation are likely to minimise the risk of infectious disease transmission.
... 2 Kimmitt and Redway studied hand drying methods by comparing paper towels, a warm air dryer and a jet air dryer for their potential to disperse viruses and contaminate the immediate environment during use. 93 They found that the use of a jet air dryer led to a significantly greater and further dispersal of microorganisms from artificially contaminated hands as com pared to paper towels and a warm air dryer. 93 Hence, it is necessary to make a careful choice of the hand drying system in healthcare settings, where the risk of cross-infection is high, especially during critical situations like the present outbreak, to safeguard patients and HCWs. ...
... 93 They found that the use of a jet air dryer led to a significantly greater and further dispersal of microorganisms from artificially contaminated hands as com pared to paper towels and a warm air dryer. 93 Hence, it is necessary to make a careful choice of the hand drying system in healthcare settings, where the risk of cross-infection is high, especially during critical situations like the present outbreak, to safeguard patients and HCWs. 92,93 It is worth noting that before wearing gloves, HCWs should dry their hands completely after hand disinfection, as residual humidity, such as that from ABHR, may increase the risk of glove perforation during daily dental care. ...
... 93 Hence, it is necessary to make a careful choice of the hand drying system in healthcare settings, where the risk of cross-infection is high, especially during critical situations like the present outbreak, to safeguard patients and HCWs. 92,93 It is worth noting that before wearing gloves, HCWs should dry their hands completely after hand disinfection, as residual humidity, such as that from ABHR, may increase the risk of glove perforation during daily dental care. 94 Lastly, for collecting used hand towels, a pedal bin installation is required near the HW set-up to avoid touching the bin, and thus to limit the risk of contamination of HCWs' hands. ...
Article
Full-text available
Healthcare-associated infections are well-studied in the literature, but remain a significant challenge for healthcare workers (HCWs) in dental practice. This type of infection is strongly correlated with the hand route of transmission of infectious agents. Thus, hand hygiene can be considered a crucial element in the prevention and control of infections.The coronavirus disease 2019 (COVID-19) outbreak is an experience of a new human coronavirus infection that has been difficult for HCWs, such as dentists and dental assistants, to control. Handwashing (HW) is a keystone method for the prevention and control of spreading severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).In healthcare settings, contrary to the general consideration of HW as a simple practice, HW is regarded as a specific procedure that should be clearly instructed to HCWs. Handwashing is based on using a correct method and the necessary equipment, and its role should be continually emphasized to reinforce compliance. Proper HW might contribute to avoiding possible cross-infection during healthcare activities, particularly in the pandemic situation.The aim of this article was to report on different HW techniques in medical and dental practice, and appropriate HW equipment to perform this simple but important procedure to prevent cross-infection, particularly during the current COVID-19 outbreak.
... A number of studies were conducted in laboratories simulating unrealistic washroom conditions, including drying of unwashed or gloved hands covered with model organism solutions (Best et al., 2014;Best and Redway, 2015). Eleven studies were assessed as good quality (Aithinne et al., 2019;Boone and Gerba, 2005;Inkinen et al., 2017;Knowlton et al., 2018;Margas et al., 2013;Mkrtchyan et al., 2013;Mohamed et al., 2015;Snelling et al., 2011;Suen et al., 2019;Verani et al., 2014;Zapka et al., 2011), 16 studies were assessed as fair quality (Boxman et al., 2009a;Breathnach et al., 2012;Carducci et al., 2016;Cooper et al., 2016;Flores et al., 2011;Gormley et al., 2017;Halabi et al., 2001;Harrison et al., 2003;Kanayama Katsuse et al., 2017;Katano et al., 2014;Kurgat et al., 2019;Patrick et al., 2010;Pitt et al., 2018;Sassi et al., 2018;Taylor et al., 2000;Tsunoda et al., 2019), and the remaining 11 studies were assessed as poor quality (Alharbi et al., 2016;Best et al., 2018;Best et al., 2014;Best and Redway, 2015;Best et al., 2012;Boxman et al., 2009a;Gerhardts et al., 2012;Huesca-Espitia et al., 2018;Kimmitt and Redway, 2016;Kouadri, 2020;Repp et al., 2013). ...
... The main reasons for poor quality classification included poor or limited description of methods (Alharbi et al., 2016;Boxman et al., 2009a;Kouadri, 2020), sub-optimal sampling methods (Alharbi et al., 2016;Huesca-Espitia et al., 2018;Kouadri, 2020); lack of significance testing (Best et al., 2012); over-interpretation of limited experimental results (Best et al., 2018;Best et al., 2014;Best and Redway, 2015); and unrealistic experimental conditions, such as results based on gloved hands (Best et al., 2014;Best and Redway, 2015;Kimmitt and Redway, 2016) which could affect the interaction between resident and transient bacteria, washing procedure and drying time. ...
... Sixteen studies identified droplets as the potential route of transmission for infectious diseases associated with bacteria (Alharbi et al., 2016;Best et al., 2018;Best et al., 2014;Best and Redway, 2015;Best et al., 2012;Carducci et al., 2016;Cooper et al., 2016;Gormley et al., 2017;Kanayama Katsuse et al., 2017;Katano et al., 2014;Kimmitt and Redway, 2016;Knowlton et al., 2018;Margas et al., 2013;Sassi et al., 2018;Taylor et al., 2000;Verani et al., 2014). Details of microbial species First flush: reduced by~3 logs After 3 flushes: reduced bỹ 4-5 logs Floor: usually 1 or 2 CFU (max 4 CFU). ...
... Por el contrario, el SMAC dispersó 167 menos veces que el SMTJ y las toallas de papel dispersaron 8 340 menos que el SMTJ. 6 Cuando los tres dispositivos de secado de manos (SMTJ, SMAC y toallas de papel) se compararon en este estudio, hubo claras diferencias en el alcance de dispersión de microorganismos, transferidos a las placas de agar fijadas en diferentes alturas y distancias, desde el secador de manos a los dispositivos de secado, y también Diferentes tipos de secadores de manos. A y B. Secador de manos de aire caliente. ...
... Cabe señalar que las diferencias en los resultados entre los tres tipos de secado de manos analizados pueden explicarse en gran medida por sus mecanismos: las toallas de papel eliminan el agua por absorción y los SMAC principalmente por evaporación, mientras que los SMTJ lo hacen mediante fuerzas de cizallamiento y dispersión en el aire; 6 más específicamente, el uso de toallas de papel produce relativamente poco movimiento de aire, los SMAC producen más (principalmente hacia abajo) y los SMTJ generan velocidades superiores a 600 kilómetros por hora (km/h), con un movimiento de aire que sale de la cámara del dispositivo de manera lateral. [6][7][8] Se ha utilizado un modelo de bacteriófago para demostrar la aerosolización y dispersión por los tres métodos de secado de manos, el cual deja ver las implicaciones para la transmisión de los patógenos en los baños de manera muy clara. Los resultados, en principio, sugieren que la infección cruzada es un factor de suma importancia en los lugares destinados para la higiene. ...
... Los resultados, en principio, sugieren que la infección cruzada es un factor de suma importancia en los lugares destinados para la higiene. 6 Los secadores más modernos expulsan flujos de aire a alta velocidad (entre 400 m/h y 640 km/h), capaces de propagar microorganismos a una distancia de hasta dos metros desde el dispositivo, lo que incrementa en gran medida el riesgo de contaminación. Dentro de los servicios de aseo suelen instalarse estos dispositivos a una distancia de 50 cm entre uno y otro, lo que produce una transferencia de microorganismos acumulada cuando dos usuarios se secan las manos al mismo tiempo, llegándose a detectar hasta 10 000 UFC por centímetro cuadrado en su interior; para tener una idea más clara de esta cifra, la carga de microorganismos detectada en la tapa de un retrete en un centro de trabajo es de 50 UFC. ...
Article
Full-text available
dispersores de patógenos para el ser humano y su entorno SECADORES DE MANOS: abstract resumen palabras clave key words Los secadores de manos de aire caliente son dis-positivos que han sido utilizados de manera am-plia en áreas públicas como hospitales, centros comerciales o estaciones de servicio. Son conside-rados un medio más económico respecto al uso de toallas comunes; sin embargo, se ha planteado que los secadores de manos pueden liberar bacterias al aire mediante el frotado de manos después del la-vado. En el presente artículo se muestra la eviden-cia acumulada sobre este tema, poniendo especial énfasis en los mecanismos por los cuales se puede crear contaminación cruzada y los microorganis-mos que pueden ser dispersados mediante estos dispositivos. Hot air hand dryers are devices that have been widely used in public areas such as hospitals, shopping centers or service stations. They are considered a more economical means compared to the use of common towels; however, it has been suggested that hand dryers can release bacteria into the air by rubbing hands after washing. This article shows the accumulated evidence on this subject , placing special emphasis on the mechanisms by which cross contamination can be created and the microorganisms that can be dispersed by these devices. Secadores de manos de aire caliente, microorga-nismos, toallas de papel, lavado de manos, servicios sanitarios. Hot air hand dryers, microorganisms, paper towels, hand washing, sanitation.
... Many jet air dryers (e.g., the Dyson Airblade™) are marketed as designed with a highefficiency particulate air (HEPA) filter built into the airflow system, which reduces the risk of redistribution of airborne microbes to the hands [38]. However, there is concern about the propensity of such rapid air movement to aerosolize microbes from users' hands or the surrounding environment, as evidenced by the number of studies examining the dispersal of microbial suspensions or some proxy thereof by such devices [39,153,160,161,163]. Particular attention has been paid to the distance such rapid air movement is capable of dispersing potentially contaminated droplets from the hands, though methods typically employed unrealistic microbial loads, or artificial proxies such as paint [39,160,161,163]. ...
... Many jet air dryers (e.g., the Dyson Airblade™) are marketed as designed with a highefficiency particulate air (HEPA) filter built into the airflow system, which reduces the risk of redistribution of airborne microbes to the hands [38]. However, there is concern about the propensity of such rapid air movement to aerosolize microbes from users' hands or the surrounding environment, as evidenced by the number of studies examining the dispersal of microbial suspensions or some proxy thereof by such devices [39,153,160,161,163]. Particular attention has been paid to the distance such rapid air movement is capable of dispersing potentially contaminated droplets from the hands, though methods typically employed unrealistic microbial loads, or artificial proxies such as paint [39,160,161,163]. ...
... Drying with paper towels is the method recommended for healthcare workers by both the Centers for Disease Control and Prevention [17] and the WHO [3], due in large part to bulk bacterial count data indicating that paper towels are effective at removing surface bacteria [48,144,147,149,157,160,164]. Use of paper towels is also associated with only minimal spread of droplets from the hands into the environment [39, 160,161,163,165,166], though it is possible that waste paper towels may serve as a bacterial reservoir [150,153]. Additionally, there is great variance in the manufacture and storage of paper towels, which may lead to risk of contamination as part of the manufacturing process, particularly of recycled paper towels [166]. ...
Preprint
The concept of hygiene is rooted in the relationship between cleanliness and the maintenance of good health. Since the widespread acceptance of the germ theory of disease, hygiene has become increasingly conflated with that of sterilization. Recent research on microbial ecology is demonstrating that humans have intimate and evolutionarily significant relationships with a diverse assemblage of microorganisms (our microbiota ). Human skin is home to a diverse, skin habitat specific community of microorganisms; this includes members that exist across the ecological spectrum from pathogen through commensal to mutualist. Most evidence suggests that the skin microbiota is likely of direct benefit to the host, and only rarely exhibits pathogenicity. This complex ecological context suggests that the conception of hygiene as a unilateral reduction or removal of microbes has outlived its usefulness. As such, we suggest the explicit definition of hygiene as ‘ those actions and practices that reduce the spread or transmission of pathogenic microorganisms, and thus reduce the incidence of disease ’. To examine the implications of this definition, we review the literature related to hand drying as an aspect of hand hygienic practice. Research on hand drying generally focuses on ‘hygienic efficacy’, a concept not typically defined explicitly, but nearly always including alterations to bulk microbial load. The corresponding literature is differentiable into two divisions: research supporting the use of forced air dryers, which typically includes effectiveness of drying as an aspect of hygienic efficacy; and research supporting the use of paper towels, which typically includes risk of aerosolized spread of microbes from hands as an aspect of hygienic efficacy. Utilizing a definition of hygiene that explicitly relies on reduction in disease spread rather than alterations to bulk microbial load would address concerns raised on both sides of the debate. Future research should take advantage of cultivation-independent techniques, working to bridge the gap between the two existing divisions of research by using health outcomes (such as the spread of disease) as dependent variables, taking into account the microbial community context of the skin microbiota, and focusing on understanding the relative contribution of bioaerosols and residual moisture to the risk of disease transmission.
... Factors associated with the choice of hand-drying method include the availability of the method, the possibility of minimizing contact with the surrounding surfaces, the perception and the rapidity of the method [40]. On the other hand, there are studies showing that, instead of electric dryers, the use of paper towels reduces the spread of bacteria, recommended in hospitals or in areas at high risk of cross-contamination, [41]. In recent years, a new version of the hot air dryer has been introduced, the air-jet dryer with antibacterial filter. ...
Article
Full-text available
Background and Objectives: The basis of any infection control program is hand hygiene (HH). The aim of this study was to investigate knowledge of HH among medical students. Materials and Methods: Students were randomly selected from two Romanian universities and a cross-sectional, questionnaire-based study was conducted between January and May 2021. The answers regarding demographic data and knowledge concerning the methods, the time and the antiseptics used for HH were collected. The selection of the study group was made according to selection criteria in accordance with ethical issues. A descriptive statistical analysis was performed, and a chi-square test was used for data comparison, with a cut-off point of 0.05 for statistical significance. Results: The results indicated that the attitude of the students towards the practice of HH improved significantly. Most students believe that simple HH can control infections. Significant differences were found by the year of study in terms of the hand surfaces included and recommended duration (p < 0.05). Conclusions: In conclusion, the study shows that most respondents have sufficient knowledge on HH, meaning that a higher compliance is required to control infections. The indicated reasons of non-compliance with HH are emergencies and other priorities.
... The proper use of a clean paper towel (patting the surface of the skin rather than rubbing it) can contribute to the removal function of hand washing, and does so in a manner which leads to less contamination of the washroom environment (Huang, Ma & Stack, 2012). This is because hot-air hand dryers can disperse pathogens into the air if the hand washing itself has been improperly practiced (Jumaa, 2005;Huang, Ma & Stack, 2012;Kimmitt & Redway, 2015;Del Carmen Huesca-Espitia et al., 2018;Suen et al., 2019;Gammon & Hunt, 2019). The potential for dispersion of infectious SARS-CoV-2 in restrooms by hot-air dryers has not been determined empirically. ...
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... Cases in other countries have shown that the number of bacteria scattered in the surrounding air after hand drying was 4.5 times higher for the high-speed air dryer (70.7 colony-forming units (cfu)) than for the warm air dryer (15.7 cfu) and 7 times higher than that for paper towels (2.6 cfu); moreover, it was considered advantageous to use paper towels, which have fewer droplets. 77,78 There are similar reports in Japan related to the highspeed air dryer; however, when comparing the research results with those of other countries, it has been indicated that the number of bacteria adhering to the hand (or gloves) at the beginning of the performance test was high in reports from other countries, and the initial conditions were different. 79 The report stated that the test evaluation results under conditions similar to real-life use had minimal effects on the above-mentioned three points of concern, and detailed experimental results have also been reported. ...
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Public Health Agencies worldwide (World Health Organization, U.S. Centers for Disease Prevention and Control, Chinese Center for Disease Control and Prevention, European Centre for Disease Prevention and Control, etc.) are recommending hand washing with soap and water for preventing the dissemination of SARS-CoV-2 infections. In this review, we have discussed the mechanism of decontamination by soap and water (involving both removal and inactivation), described the contribution of the various components of formulated soaps to performance as cleansers and to pathogen inactivation, explained why adherence to recommended contact times is critical, evaluated the possible contribution of water temperature to inactivation, discussed the advantages of antimicrobial soaps versus basic soaps, discussed the differences between use of soap and water versus alcohol-based hand sanitizers for hand decontamination, and evaluated the limitations and advantages of different methods of drying hands following washing. While the paper emphasizes data applicable to SARS-CoV-2, the topics discussed are germane to most emerging and re-emerging enveloped and non-enveloped viruses and other pathogens.
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The Guideline for Hand Hygiene in Health-Care Settings provides health-care workers (HCWs) with a review of data regarding handwashing and hand antisepsis in health-care settings. In addition, it provides specific recommendations to promote improved hand-hygiene practices and reduce transmission ofpathogenic microorganisms to patients and personnel in health-care settings. This report reviews studies published since the 1985 CDC guideline (Garner JS, Favero MS. CDC guideline for handwashing and hospital environmental control, 1985. Infect Control 1986;7:231-43) and the 1995 APIC guideline (Larson EL, APIC Guidelines Committee. APIC guideline for handwashing and hand antisepsis in health care settings. Am J Infect Control 1995;23:251-69) were issued and provides an in-depth review of hand-hygiene practices of HCWs, levels of adherence of personnel to recommended handwashing practices, and factors adversely affecting adherence. New studies of the in vivo efficacy of alcohol-based hand rubs and the low incidence of dermatitis associated with their use are reviewed. Recent studies demonstrating the value of multidisciplinary hand-hygiene promotion programs and the potential role of alcohol-based hand rubs in improving hand-hygiene practices are summarized. Recommendations concerning related issues (e.g., the use of surgical hand antiseptics, hand lotions or creams, and wearing of artificial fingernails) are also included.
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Efficient washing and drying of hands is important in prevention of the transfer of micro-organisms. However, knowledge surrounding the potential for microbial contamination according to hand-drying methods is limited. This study assessed the potential for airborne microbe dispersal during hand drying by four methods (paper towels, roller towel, warm air and jet air dryer) using three different models. The jet air dryer dispersed liquid from users' hands further and over a greater range (up to 1.5m) than the other drying methods (up to 0.75m), demonstrating the differing potential risks for airborne microbe dissemination, particularly if handwashing is suboptimal. Copyright © 2015 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.
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Background The efficiency of hand drying is important in preventing pathogen spread, but knowledge surrounding which drying methods contribute least towards contamination of the environment and users is limited. Aim To compare the propensity of three common hand-drying methods (jet air, warm air dryers, and paper towels) to contaminate the environment, users, and bystanders. Methods Hands were coated in lactobacilli to simulate poorly washed, contaminated hands, and dried. The investigation comprised 120 air-sampling tests (60 tests and 60 controls), divided into close and 1 m proximity from the drying process. Separate tests used hands coated in paint to visualize droplet dispersal. Findings Air bacterial counts in close proximity to hand drying were 4.5-fold higher for the jet air dryer (70.7 cfu) compared with the warm air dryer (15.7 cfu) (P = 0.001), and 27-fold higher compared with use of paper towels (2.6 cfu) (P < 0.001). Airborne counts were also significantly different during use of towel drying versus warm air dryer (P = 0.001). A similar pattern was seen for bacterial counts at 1 m away. Visualization experiments demonstrated that the jet air dryer caused the most droplet dispersal. Conclusion Jet air and warm air dryers result in increased bacterial aerosolization when drying hands. These results suggest that air dryers may be unsuitable for use in healthcare settings, as they may facilitate microbial cross-contamination via airborne dissemination to the environment or bathroom visitors.
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Infectious diseases (ID) circulating in the home and community remain a significant concern. Several demographic, environmen- tal, and health care trends, as reviewed in this report, are combining to make it likely that the threat of ID will increase in coming years. Two factors are largely responsible for this trend: first, the constantly changing nature and range of pathogens to which we are exposed and, secondly, the demographic changes occurring in the community, which affect our resistance to infection. This report reviews the evidence base related to the impact of hand hygiene in reducing transmission of ID in the home and community. The report focuses on developed countries, most particularly North America and Europe. It also evaluates the use of alcohol-based hygiene procedures as an alternative to, or in conjunction with, handwashing. The report compiles data from intervention studies and considers it alongside risk modeling approaches (both qualitative and quantitative) based on microbiologic data. The main conclusions are as follows: (1) Hand hygiene is a key component of good hygiene practice in the home and community and can produce significant benefits in terms of reducing the incidence of infection, most particularly gastrointestinal infections but also respiratory tract and skin infections. (2) Decontamination of hands can be carried out either by handwashing with soap or by use of waterless hand sanitizers, which reduce contamination on hands by removal or by killing the organisms in situ. The health impact of hand hygiene within a given community can be increased by using products and procedures, either alone or in sequence, that maximize the log reduction of both bacteria and viruses on hands. (3) The impact of hand hygiene in reducing ID risks could be increased by convincing people to apply hand hygiene procedures correctly (eg, wash their hands correctly) and at the correct time. (4) To optimize health benefits, promotion of hand hygiene should be accompanied by hygiene education and should also involve promotion of other aspects of hygiene. (Am J Infect Control 2007;35:S27-64.)
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Aims: This study compared the potential for cross contamination of the surrounding environment resulting from two different hand-drying methods: paper towels and the use of an air blade dryer. Methods and results: One hundred volunteers for each method washed their hands and dried them using one of the two methods. Bacterial contamination of the surrounding environment was measured using settle plates placed on the floor in a grid pattern, air sampling and surface swabs. Both drying methods produced ballistic droplets in the immediate vicinity of the hand-drying process. The air blade dryer produced a larger number of droplets which were dispersed over a larger area. Settle plates showed increased microbial contamination in the grid squares which were affected by ballistic droplets. Using the settle plates counts, it was estimated that approx. 1.7 × 10(5) cfu more micro-organisms were left on the laboratory floor (total area approx. 17.15 m(2)) after 100 volunteers used an air blade dryer compared to when paper towels were used. Conclusions: The two drying methods led to different patterns of ballistic droplets and levels of microbial contamination under heavy use conditions. Whilst the increase in microbial levels in the environment is not significant if only nonpathogenic micro-organisms are spread, it may increase the risk of pathogen contamination of the environment when pathogens are occasionally present on people's hands. Significance and impact of the study: The study suggests that the risk of cross contamination from the washroom users to the environment and subsequent users should be considered when choosing a hand-drying method. The data could potentially give guidance following the selection of drying methods on implementing measures to minimise the risk of cross contamination.
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The transmission of bacteria is more likely to occur from wet skin than from dry skin; therefore, the proper drying of hands after washing should be an integral part of the hand hygiene process in health care. This article systematically reviews the research on the hygienic efficacy of different hand-drying methods. A literature search was conducted in April 2011 using the electronic databases PubMed, Scopus, and Web of Science. Search terms used were hand dryer and hand drying. The search was limited to articles published in English from January 1970 through March 2011. Twelve studies were included in the review. Hand-drying effectiveness includes the speed of drying, degree of dryness, effective removal of bacteria, and prevention of cross-contamination. This review found little agreement regarding the relative effectiveness of electric air dryers. However, most studies suggest that paper towels can dry hands efficiently, remove bacteria effectively, and cause less contamination of the washroom environment. From a hygiene viewpoint, paper towels are superior to electric air dryers. Paper towels should be recommended in locations where hygiene is paramount, such as hospitals and clinics.
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Gastro-intestinal infections are widespread in the community and have considerable economic consequences. In this study, we followed chains of infection from a public toilet scenario, looking at infection risks by correlating the transmission of bacteria, fungi and viruses to our current knowledge of infectious doses. Transmission of Escherichia coli, Bacillus atrophaeus spores, Candida albicans and bacteriophage MS2 from hands to surfaces was examined in a transmission model, that is toilet brush, door handle to water tap. The load of viable pathogens was significantly reduced during transfer from hands to objects. Nevertheless, it was shown that pathogens were successfully transferred to other people in contagious doses by contact with contaminated surfaces. Our results suggest that infection risks are mainly dependent on current infectious doses of pathogens. For enteritic viruses or bacteria, for example Norovirus or EHEC, only a few particles or cells are sufficient for infection in public lavatories, thus bearing a high risk of infection for other persons. However, there seems to be only a low probability of becoming infected with pathogens that have a high infectious dose whilst sharing the same bathroom. The transmission model for micro-organisms enables a risk assessment of gastro-intestinal infections on the basis of a practical approach.