Estimating foodborne gastroenteritis, Australia.
ABSTRACT We estimated for Australia the number of cases, hospitalizations, and deaths due to foodborne gastroenteritis in a typical year, circa 2000. The total amount of infectious gastroenteritis was measured by using a national telephone survey. The foodborne proportion was estimated from Australian data on each of 16 pathogens. To account for uncertainty, we used simulation techniques to calculate 95% credibility intervals (CrI). The estimate of incidence of gastroenteritis in Australia is 17.2 million (95% confidence interval 14.5-19.9 million) cases per year. We estimate that 32% (95% CrI 24%-40%) are foodborne, which equals 0.3 (95% CrI 0.2-0.4) episodes per person, or 5.4 million (95% CrI 4.0-6.9 million) cases annually in Australia. Norovirus, enteropathogenic Escherichia coli, Campylobacter spp., and Salmonella spp. cause the most illnesses. In addition, foodborne gastroenteritis causes approximately 15,000 (95% CrI 11,000-18,000) hospitalizations and 80 (95% CrI 40-120) deaths annually. This study highlights global public health concerns about foodborne diseases and the need for standardized methods, including assessment of uncertainty, for international comparison.
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ABSTRACT: 1857 Foodborne disease is a major public health problem worldwide. To examine changes in foodborne illness in Australia, we estimated the incidence, hospitalizations, and deaths attributed to contaminated food circa 2010 and re-calculated estimates from circa 2000. Approximately 25% of gastroenteritis cases were caused by contaminated food; to account for uncertainty we used simulation techniques to estimate 90% credible intervals. We estimate that circa 2010, 4.1 million foodborne gastroenteritis cases occurred, and circa 2000, 4.3 million cases occurred. Circa 2010, con-taminated food was estimated to be responsible for 30,840 gastroenteritis-associated hospitalizations, 76 associated deaths, and 5,140 nongastrointestinal illnesses. Cases of salmonellosis and campylobacteriosis increased from 2000 to 2010 and were the leading causes of gastroenteritis-associated hospitalizations; Listeria monocytogenes and nontyphoidal Salmonella spp. infections were the leading causes of death. Although the overall incidence of food-borne illnesses declined over time in Australia, cases of foodborne gastroenteritis are still common. F oodborne illness is a major public health problem and a common cause of illness and death worldwide. Out-breaks linked to contaminated food can affect the public's trust and financially harm implicated businesses and as-sociated food industries. Estimates of the effects of food-borne illnesses and individual pathogens provide evidence for policy interventions and food safety regulation. In addi-tion, estimates of changes in the incidence of foodborne ill-nesses and hospitalizations over time provide information on the effectiveness of changes to food safety standards and regulation. Many agents can cause foodborne illness; some of these agents are transmitted to humans by other routes as well as by food. Most foodborne illnesses manifest as gas-troenteritis, but other presentations, such as meningitis and hepatitis may also result from infection, and sequelae may occur weeks after the acute infection. Many countries have estimated the incidence of foodborne diseases (1–5). In Australia in 2000, foodborne incidence, hospitalizations, and deaths were estimated to cost 1.25 billion Australian dollars annually (6,7). How-ever, since 2000, surveillance has substantially improved, data availability has increased, and methods have been refined. To inform current public health decisions and policies in Australia, we used new methods and datasets to estimate the incidence of infectious gastroenteritis and associated hospitalizations and deaths in Australia circa 2010. We then applied these refined methods to circa 2000 data so that estimates from the 2 periods could be directly compared.Emerging Infectious Diseases 11/2014; 20(11):1857. · 7.33 Impact Factor
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ABSTRACT: The purpose of this study was to firstly design an intervention to decrease cross-contamination in the home by the development of the habitual behavior of microwaving the dishcloth/sponge and secondly to determine if this behavior could be maintained over time. Participants were randomly assigned to either a high-frequency or low-frequency reminder habit building condition or a control condition. Results indicated that for both habit building conditions, food-safety behavior significantly increased compared to the control group and these changes were maintained at follow-up. Additionally, improvement in behavior was mediated by increase in habit strength. The major conclusion of this study is that providing a cue to action and reminders build food-safety habits that result in changes in food-safety behaviors. This has major implications for other food-safety interventions.Food Research International 12/2014; · 3.05 Impact Factor
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ABSTRACT: Foodborne disease is a major public health problem worldwide. To examine changes in foodborne illness in Australia, we estimated the incidence, hospitalizations, and deaths attributed to contaminated food circa 2010 and recalculated estimates from circa 2000. Approximately 25% of gastroenteritis cases were caused by contaminated food; to account for uncertainty we used simulation techniques to estimate 90% credible intervals. We estimate that circa 2010, 4.1 million foodborne gastroenteritis cases occurred, and circa 2000, 4.3 million cases occurred. Circa 2010, contaminated food was estimated to be responsible for 30,840 gastroenteritis-associated hospitalizations, 76 associated deaths, and 5,140 nongastrointestinal illnesses. Cases of salmonellosis and campylobacteriosis increased from 2000 to 2010 and were the leading causes of gastroenteritis-associated hospitalizations; Listeria monocytogenes and nontyphoidal Salmonella spp. infections were the leading causes of death. Although the overall incidence of foodborne illnesses declined over time in Australia, cases of foodborne gastroenteritis are still common.Emerging infectious diseases 11/2014; 20(11):1857-64. · 7.33 Impact Factor
We estimated for Australia the number of cases, hos-
pitalizations, and deaths due to foodborne gastroenteritis in
a typical year, circa 2000. The total amount of infectious
gastroenteritis was measured by using a national tele-
phone survey. The foodborne proportion was estimated
from Australian data on each of 16 pathogens. To account
for uncertainty, we used simulation techniques to calculate
95% credibility intervals (CrI). The estimate of incidence of
gastroenteritis in Australia is 17.2 million (95% confidence
interval 14.5–19.9 million) cases per year. We estimate that
32% (95% CrI 24%–40%) are foodborne, which equals 0.3
(95% CrI 0.2–0.4) episodes per person, or 5.4 million (95%
CrI 4.0–6.9 million) cases annually in Australia. Norovirus,
enteropathogenic Escherichia coli, Campylobacter spp.,
and Salmonella spp. cause the most illnesses. In addition,
foodborne gastroenteritis causes ≈15,000 (95% CrI
11,000–18,000) hospitalizations and 80 (95% CrI 40–120)
deaths annually. This study highlights global public health
concerns about foodborne diseases and the need for stan-
dardized methods, including assessment of uncertainty, for
Outbreaks are more likely to be far reaching, and some are
even global in scale because of widespread food distribu-
tion and changes in methods of food preparation (1).
Further changes in the incidence of foodborne disease and
the pattern of food-related illness can be anticipated from
global warming (2). As a result of changed conditions in
food production and better laboratory detection tech-
niques, new foodborne pathogens continue to be identified
he pattern of foodborne disease has changed substan-
tially in industrialized countries in recent decades.
(3). In particular, we are now faced with the emergence of
antimicrobial drug–resistant bacteria and a number of
viruses not previously recognized (4,5).
Foodborne disease is a public health concern in all parts
of the world. In the United States, foodborne disease caus-
es an estimated 76 million illnesses, 325,000 hospitaliza-
tions, and 5,000 deaths each year (6). In the United
Kingdom, an estimated 2.37 million cases of foodborne
gastroenteritis occurred in 1995 (7). Previous estimates of
foodborne gastroenteritis in Australia have ranged from
1–2 million (8) to 4 million episodes per year (9). The
effect of such large numbers of persons with gastrointesti-
nal illness is considerable. Arecent national survey of gas-
troenteritis in Australia found that one third of working
adults miss >1 days of work when they have gastroenteri-
tis, and another third of cases result in a caregiver missing
work (10). In Australia in 2003, 99 reported outbreaks of
foodborne disease affected 1,686 people and caused 6
deaths (11). Any evidence of food contamination can also
have a major effect on food industry and trade. The food
industry in Australia generates >$29 billion in food pro-
duction, with >20% of products exported, and $57 billion
in food processing (12).
Transmission of Pathogens Causing Gastroenteritis
Infectious gastroenteritis is caused by many pathogens,
each with unique characteristics requiring different labora-
tory tests for identification. Transmission of pathogens to
humans may occur from contaminated foods or water, or
from infected persons, environments, or animals. Some
pathogens that cause gastroenteritis, such as Bacillus
cereus, are always thought to be the result of contaminat-
ed food, whereas others, such as rotavirus, are largely
transmitted by nonfoodborne routes. Most enteric
pathogens have multiple modes of transmission (13).
Many clinical cases of gastroenteritis are assessed as
“presumed infectious” and do not have a pathogen isolat-
ed, even when a stool sample is tested (14). These include
Gillian Hall,* Martyn D. Kirk,† Niels Becker,* Joy E. Gregory,‡ Leanne Unicomb,§ Geoffrey Millard,¶
Russell Stafford,# Karin Lalor,‡ and the OzFoodNet Working Group
Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 11, No. 8, August 2005 1257
*Australian National University, Canberra, Australian Capital
Territory (ACT), Australia; †OzFoodNet, Canberra, ACT, Australia;
‡Department of Human Services, Melbourne, Victoria, Australia;
§Hunter Population Health Unit, Wallsend, New South Wales,
Australia; ¶ACT Analytical Laboratory, Weston Creek, ACT,
Australia; and #Queensland Health, Archerfield, Queensland,
cases in which a known pathogen is present but is not iden-
tified and cases in which the pathogen is totally unknown
(15). Numerous pathogens that were unknown only a few
decades ago are now considered commonplace, including
Campylobacter spp., Shiga toxin–producing Escherichia
coli, and norovirus (16). More unknown pathogens are
likely to be major causes of illness, some of which will
become apparent with time and investigation.
Estimating the Level of
As part of the activities of OzFoodNet, the foodborne
disease surveillance network operating in Australia since
2000, we undertook a study to estimate the amount of
foodborne gastroenteritis in contemporary Australia. In the
absence of an internationally agreed-upon methodology,
the approach used in the United States provided the best
method for obtaining internationally comparable estimates
(6). Two components are required to estimate the extent of
foodborne gastroenteritis by this method: 1) the total
amount of gastroenteritis in the country and 2) the propor-
tion of gastroenteritis that is foodborne. The product of
these 2 estimates gives the total number of cases of food-
Uncertainty is inherent in data used in such calcula-
tions. Variability may be quantified by statistical concepts
like standard error and confidence intervals, but other
components of uncertainty are due to paucity of data.
Since some information is always available, however, we
can quantify each component of uncertainty by a plausible
probability distribution using all relevant information
available. We can then use simulations of these distribu-
tions to generate an interval that contains the credible esti-
mates of the number of foodborne cases of gastroenteritis.
These interval estimates are akin to credibility intervals
used in Bayesian inferences.
Our objective for this study was to use Australian data
to calculate the number of cases, hospitalizations, and
deaths due to foodborne gastroenteritis in Australia in a
typical year, around the year 2000, accounting for uncer-
tainty in the estimate.
The calculations to estimate incidence, hospitalizations,
and deaths are described below and in the Figure. Details
of the data sources and the simulation technique used to
account for uncertainty are shown in the online Appendix
(available from http://www.cdc.gov/ncidod/EID/vol11
We considered the definition of foodborne to include
any infectious gastroenteritis caused by eating food,
including food contaminated just before eating. The pro-
portion of infectious gastroenteritis cases that are due to
foodborne transmission in the community and their pro-
portion among hospitalizations and deaths, were assessed
by using data from multiple Australian sources about indi-
vidual known pathogens.
Gastroenteritis caused by known pathogens was studied
to estimate the proportion of all infectious gastroenteritis
that is foodborne. Of 25 pathogens with the potential for
foodborne transmission, 16 (those listed in Table 1) were
considered relevant. Pathogens not considered relevant
were either not foodborne (Clostridium difficile), did not
cause gastroenteritis (Brucella spp., Listeria spp.,
Toxoplasma gondii, hepatitis A virus), or were only
acquired overseas (Salmonella Typhi, Vibrio cholerae,
Cyclospora cayetanensis, Trichinella spiralis).
For each of the 16 pathogens, yearly estimates were
made of the total number of cases of gastroenteritis in the
community; this number was based on data collected in the
National Notifiable Diseases Surveillance System, pub-
lished results from the Water Quality Study conducted in
Melbourne in 1998 (17,18), laboratory data, or outbreak
data. Necessary adjustments were made for underreporting
in the Australian surveillance system, incomplete popula-
tion coverage, and the proportion of infections acquired
overseas (online Appendix). We also estimated, for each of
the pathogens, the total number of hospitalizations and
deaths based on data from the National Hospital Morbidity
Database (NHMD) as well as the proportion of cases due
to foodborne transmission, which was estimated from out-
break data, the literature, and because Australian data were
lacking, a Delphi process involving 10 foodborne disease
experts in Australia. The number of foodborne episodes for
each pathogen was then obtained by multiplying the esti-
mate of the foodborne proportion by the estimate of the
total number of cases, hospitalizations, and deaths. The
overall proportion of infectious gastroenteritis in the com-
munity due to foodborne transmission was then estimated
by dividing the sum of the foodborne cases due to the 16
known pathogens by the sum of all cases due to the 16
known pathogens (Figure). The equivalent calculation was
also done for hospital admissions due to known pathogens
to give the proportion of hospitalizations for infectious
gastroenteritis due to foodborne transmission.
We assumed that the proportion of gastroenteritis that is
foodborne is the same among cases caused by known
pathogens as among those caused by unknown pathogens.
Adjustments were made for the proportion estimated as
acquired overseas for certain pathogens (online Appendix).
Incidence of Foodborne Gastroenteritis
The total amount of infectious gastroenteritis in
Australia in 1 year was estimated from the National
Gastroenteritis Survey 2001–2002. This computer-assisted
telephone survey ran during 12 months from September
1258Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 11, No. 8, August 2005
2001 to August 2002 in all states and territories of
Australia. Ethics clearance was obtained from the
Australian Department of Health and Ageing Ethics
Committee and from other state health departments and
university committees. Random digit dialing was used to
select households, and then the person with the most recent
birthday was selected as the respondent. The response rate
was 67%, and the final sample was 6,087 persons. Data
were collected on symptoms of gastroenteritis in the previ-
ous 4 weeks. The case definition excluded persons who
identified a noninfectious cause for their symptoms, and an
adjustment was made for persons with gastrointestinal
symptoms secondary to a respiratory infection (19). The
case definition was >3 loose stools or >2 episodes of vom-
iting or, if respiratory symptoms were present, >4 loose
stools or >3 episodes of vomiting in a 24-hour period in the
previous 4 weeks.
The final estimate of the total number of cases of food-
borne gastroenteritis in the community is the product of the
proportion foodborne and the total number of cases of
infectious gastroenteritis. The incidence per person per
year was estimated by using population data from the
Australian Bureau of Statistics (20).
Hospitalizations for Foodborne Gastroenteritis
The total number of hospitalizations for gastroenteritis
was estimated from the National Hospital Morbidity
Database (21), which records all admissions to hospital in
Australia. Data from 1993/1994 to 1998/1999 were exam-
ined for International Classification of Diseases, Ninth
Revision, Clinical Modification (ICD-9-CM) codes for
gastroenteritis as either a principal diagnosis of as any of a
further 9 additional diagnoses. Additional diagnoses refer
to cases in which gastroenteritis was a contributing factor
to, but not the only reason for, admission. These data were
used to estimate the average number of diagnoses per year
for each of 14 of the known pathogens. No ICD code for
Aeromonas infection was in the hospital separation dataset,
and hospitalizations due to E. coli infections did not distin-
guish between enteropathogenic and Shiga toxin–produc-
ing types, leading to a study of 14 rather than 16 known
pathogens in hospital data. Diagnoses coded “gastroenteri-
tis, presumed infectious” were also examined.
Adjustments were not made for underreporting of individ-
ual pathogens, since any missed diagnoses for specific
pathogens should be included in this unknown category.
The final estimate of the total number of hospitaliza-
tions due to foodborne gastroenteritis was the product of
the proportion of hospitalizations among known pathogens
that is foodborne and the total number of hospitalizations
for infectious gastroenteritis (including cases of unknown
but presumed infectious causes).
Foodborne Gastroenteritis, Australia
Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 11, No. 8, August 20051259
Deaths Due to Foodborne Gastroenteritis
Deaths in the hospital were determined for gastroenteri-
tis as either a principal diagnosis of as any of a further 9
additional diagnoses (data from 1993/1994 to 1998/1999).
The final estimate of the total number of deaths due to
foodborne gastroenteritis was the product of the proportion
foodborne and the total number of deaths in the hospital
due to infectious gastroenteritis.
Accounting for Uncertainty in Data
Where suitable data were available, 95% confidence
intervals (CI) were calculated. Otherwise, uncertainty in the
data was accounted for by using simulation techniques.
Plausible probability distributions were generated by using
all available information, and the interval between 2.5th
and 97.5th percentiles gave the 95% credible interval (95%
CrI). The median was taken as the point estimate. This tech-
nique is explained in the online Appendix. Calculations
were carried out with the Statistical Package for the Social
Sciences, version 11.50 (SPSS Inc., Chicago, IL, USA).
The case definition applied to 450 (7%) of 6,087 respon-
dents to the National Gastroenteritis Survey. When weight-
ed to the Australian population by age and sex, this number
extrapolated to 17.2 million (95% CI 14.5–19.9 million)
cases of gastroenteritis in Australia in 1 year, or 0.92 (95%
CI 0.77–1.06) cases per person per year (13). This number
includes all causes of infectious gastroenteritis.
Among the 16 known pathogens were an estimated 4.6
million (95% CrI 3.8–5.5 million) cases of gastroenteritis
due to all modes of transmission. Of these, an estimated
1.6 million (95% CrI 1.2–2.1 million ) were due to bacter-
ial infections, 2.3 million (95% CrI 1.7–2.8 million) were
due to viral infections, and 0.70 million (95% CrI
0.44–0.97 million) were due to parasites (Table 1).
Among known pathogens, 1.5 million (95% CrI
1.0–1.9 million) cases were acquired through food.
Enteropathogenic E. coli, noroviruses, Campylobacter
spp., and Salmonella spp. accounted for 88% of all food-
borne disease in this group of pathogens (Table 1). The
proportion of gastroenteritis due to foodborne transmission
was estimated at 32% (95% CrI 24–40%). The product of
the total number of cases of gastroenteritis (17.2 million;
95% CrI 14.5–19.9 million) multiplied by the proportion
that was foodborne (0.32, 95% CrI 0.24–0.40) produced an
estimate of 5.4 million cases of foodborne gastroenteritis
in 1 year in Australia (circa 2002), with a 95% CrI of
4.0–6.9 million cases.
Among hospitalizations for gastroenteritis due to the 14
known pathogens were 10,070 (95% CrI 8,630–11,470)
diagnoses of gastroenteritis; an estimated 3,640 (95% CrI
2,600–4,670) of these cases were due to eating contaminat-
ed food. The overall proportion of hospitalizations estimat-
ed to be from foodborne gastroenteritis was 0.36 (95% CrI
0.30–0.41) (Table 2).
The total number of hospital diagnoses for gastroenteri-
tis was estimated as 41,000 (95% CrI 33,000–49,000). The
number due to foodborne transmission was 14,700 (95%
CrI 11,400–18,000) (Table 3).
The NHMD 1993/1994 to 1998/1999 showed 1,302
deaths (157–311 per year) in patients with a code for a
principal or additional diagnosis of infectious gastroenteri-
tis in the 6 years. The average was 217 (standard deviation
51) per year. Of these 1,302 deaths, 287 occurred in
patients with a principal diagnosis of infectious gastroen-
teritis. Application of the proportion of hospital diagnoses
due to foodborne gastroenteritis (36%, 95% CrI
1260 Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 11, No. 8, August 2005
Figure. Scheme of data sources and calculations used to estimate
the number of cases of foodborne gastroenteritis in the communi-
ty in 1 year in Australia around the year 2000.
30%–41%) to the number of deaths in which the diagnosis
included infectious gastroenteritis (217, 95% CrI 120–320)
provided an estimate of 76 (95% CrI 41–120) deaths due
to foodborne gastroenteritis each year (Table 3).
The estimates from this study demonstrate the consid-
erable prevalence of foodborne disease in contemporary
Australia and justify the attention given to foodborne dis-
ease surveillance and food safety. The uncertainty esti-
mates indicate that even the lower boundary of the credible
interval is still high, with at least 4 million cases of food-
borne gastroenteritis, and possibly as many as 7 million
per year. This means that on average, every Australian can
expect to experience an episode of foodborne illness about
every 3 to 4 years. Hospitalizations are uncommon at 8 per
10,000 people each year, and ≈4 deaths per million persons
occur per year.
Similar studies have been done in United States (6) and
the United Kingdom (7). The Australian estimate of inci-
dence is remarkably similar to that reported for the United
States, but higher than in the United Kingdom. In the
United States, 36% of all gastroenteritis was estimated to
be due to foodborne transmission, and incidence was esti-
mated at 0.28 cases per person per year. In the United
Kingdom, 26% of gastroenteritis was estimated to be due
to foodborne transmission, and incidence was estimated at
0.04 cases per person per year in 1995. The importance of
using a standardized method when comparing results of
the amount of foodborne gastroenteritis across countries or
times cannot be overemphasized. Evidence suggests that a
prospective cohort study design may produce a lower inci-
dence of community gastroenteritis than a cross-sectional
design. The UK study included a quality control substudy
to compare the incidence based on a retrospective recall
method with incidence from a prospective diary method;
the estimates of incidence were 0.6 and 0.2 cases per per-
son per year, respectively (14). Prospective studies that
require participants to supply a stool sample every time
they report gastroenteritis might tend to cause an underes-
timate because of unwillingness to provide a sample; on
the other hand, in a retrospective recall method, respon-
dents might “telescope” events into a shorter time frame. A
prospective study done in the Netherlands (22) also found
Foodborne Gastroenteritis, Australia
Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 11, No. 8, August 20051261
a lower incidence than that seen in the United Kingdom.
Other variations in methods also exist across countries,
such as differences in surveillance systems and the quality
of outbreak data available to estimate the proportion of
cases that are foodborne. Not only may the study design
influence the final estimate, but also the definition of gas-
troenteritis. Even a seemingly small difference in the defi-
nition of gastroenteritis can lead to a considerable
difference in the final estimates (23).
The definition of community gastroenteritis used in this
Australian study refers to moderate-to-severe illness, with
at >3 loose stools or >2 episodes of vomiting in a single
day. To improve the specificity of our definition for enteric
illness, we excluded patients with concomitant respiratory
symptoms unless they had more severe symptoms of diar-
rhea or vomiting. Previous studies have found similarly
high rates of respiratory symptoms amongst cases of gas-
troenteritis (24). A definition inclusive of milder illness
would lead to a higher estimate of foodborne gastroenteri-
tis, and a definition that included only more severe illness
would lead to a lower estimate.
We also took account of those with concurrent respira-
tory symptoms in our definition of community gastroen-
teritis, although most studies estimating the amount of
gastroenteritis have not considered this. The United States
study (6) adjusted for those with respiratory illness by
excluding a proportion of case-patients who were thought
likely to have symptoms secondary to respiratory infec-
tions rather than a primary enteric infection. The UK defi-
nition of gastroenteritis was different from the Australian
definition in several ways. While differing arguments can
be raised about the best definition of gastroenteritis, the
main concern is to have a consistent, reasonable definition
for comparative purposes.
Of the 5.4 million (95% CrI 4.0–6.9 million) cases of
foodborne gastroenteritis, 28% were attributed to known
pathogens. This finding compares with 18% in the United
States (6) and 41% in the United Kingdom (7). The
Australian data used to estimate the pathogen-specific
numbers of community cases of gastroenteritis were vari-
able in quality. Salmonella notifications have been rela-
tively stable over the last 5 years, and characteristics of
this illness are fairly well understood. In comparison,
reports of illness due to Campylobacter have increased
steadily during the same time (25). This finding could be
due to reporting artifacts or increasing infection rates in the
community. The diagnostic laboratory tests have not
changed appreciably during this time.
The pathogen-specific estimates in this study that most
influenced the final estimate of the proportion of gastroen-
teritis that is foodborne were those for norovirus and
enteropathogenic E. coli, as these accounted for the largest
numbers. The estimates for both were determined from a
high-quality longitudinal study (17). Nevertheless, the
sample was limited to a specific subpopulation and geo-
graphic location. The high proportion of E. coli is similar
to findings in the United Kingdom, although we estimated
that 50% of cases caused by this pathogen were foodborne
compared to 8% of cases in the UK assessment (7) and
30% in the United States (6). In recent years, the capacity
of laboratories to identify noroviruses with polymerase
chain reaction tests has improved considerably, and this
virus is likely to become increasingly recognized (26).
Factors were used to adjust for underreporting when
using data from outbreaks and surveillance. Further stud-
ies are needed to give more robust estimates of the level of
underreporting compared with the true level in the commu-
nity. The estimates of the proportion of illness due to food-
borne transmission for specific pathogens relied largely on
outbreak data and opinions of foodborne diseases experts.
Outbreak data can be very sensitive to the outcomes from
larger events, which could bias the estimate of the propor-
tion foodborne in either direction (27). Foodborne disease
experts’ experience was based on pathogen characteristics
in the laboratory, results of outbreak investigations, and
knowledge from case-control studies of sporadic infec-
tions. For pathogens estimated to have a large number of
cases, such as norovirus, the estimate of the proportion
thought to be foodborne can influence the final estimate.
Both the UK and Australian estimates were based on out-
break data, but only 11% of Norwalk-like virus (cali-
civiruses) gastroenteritis was ascribed to foodborne
transmission in the UK study, compared with 40% in the
United States, and 25% in Australia (6,7). These individual
1262Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 11, No. 8, August 2005
estimates had some influence on the final estimates of the
proportion of all gastroenteritis that is foodborne.
Hospital data in Australia are fairly complete, and only
a few hospitals, mostly private, have not contributed
records of all admissions to the national database in the last
decade (21). Coding of admissions varies over time and
place, but a patient with gastroenteritis is likely to be
coded for this condition in the first 10 diagnoses (28).
Approximately two thirds of diagnoses were coded as the
main reason for admission. Additional diagnoses may rep-
resent cases with complications or comorbidity that took
precedence in the order of coding or cases acquired in the
hospital. Some deaths due to gastroenteritis may have
occurred in nursing homes, which were not included.
Among the known pathogens, bacterial infections account-
ed for >90% of hospital admissions in Australia, which is
similar to the proportion in the United Kingdom (7) but
higher than the 60% estimated in the United States (6).
Campylobacteriosis followed by salmonellosis accounted
for most admissions due to bacterial infections in Australia
and the United Kingdom; in the United States this order
was reversed. These illnesses are important when consid-
ering the severe end of the spectrum of foodborne gas-
We used the best available Australian data to conduct
this study, but as experienced by others conducting
research overseas, the quality of the data inevitably varied.
Since the quality of the data cannot be easily improved, we
chose to provide estimates that reflect the true state of
uncertainty of the data by using a simulation technique that
can be easily applied. Taking account of uncertainty
informs the data users, including policy makers, that a very
precise estimate is not possible. An appreciation of the
degree of confidence that can be placed in an estimate is an
important part of the responsible presentation of results
that may have considerable effects at a policy level. With
these stipulations, we are confident that the level of food-
borne gastroenteritis is high in Australia. In the future,
improvements in data completeness and quality would
enhance the robustness of the calculations, but estimates of
uncertainty are likely to remain an important component of
We thank Edmond Hsu for assistance with statistics; Scott
Cameron, Mark Veitch, Craig Dalton, and Rod Givney for assis-
tance with the Delphi process to assess the pathogen-specific pro-
portion of foodborne illness; Scott Cameron, Mark Veitch, and
Tom Ross for helpful comments on the manuscript; and the
OzFoodNet Working Group, including Jane Raupach, Rosie
Ashbolt, Jennie Musto, and Mohinder Sarna.
OzFoodNet and this project are funded by the Australian
Government Department of Health and Ageing.
Dr. Hall is a lecturer in the Master of Applied Epidemiology
program at Australian National University. She has interests in
foodborne disease and nutrition, climate change, and indigenous
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Address for correspondence: Gillian Hall, National Centre for
Epidemiology and Population Health, Australian National University,
Australian Capital Territory 0200, Australia; fax: 61-2-6125-0740; email:
1264 Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 11, No. 8, August 2005