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RESEARC H ARTIC LE Open Access
Clinical outcomes of seasonal influenza and
pandemic influenza A (H1N1) in pediatric
inpatients
Pranita D Tamma
1*
, Alison E Turnbull
2
, Aaron M Milstone
1
, Sara E Cosgrove
3
, Alexandra Valsamakis
4
, Alicia Budd
5
,
Trish M Perl
6
Abstract
Background: In April 2009, a novel influenza A H1N1 (nH1N1) virus emerged and spread rapidly worldwide. News
of the pandemic led to a heightened awareness of the consequences of influenza and generally resulted in
enhanced infection control practices and strengthened vaccination efforts for both healthcare workers and the
general population. Seasonal influenza (SI) illness in the pediatric population has been previously shown to result in
significant morbidity, mortality, and substantial hospital resource utilization. Although influenza pandemics have the
possibility of resulting in considerable illness, we must not ignore the impact that we can experience annually
with SI.
Methods: We compared the outcomes of pediatric patients ≤18 years of age at a large urban hospital with
laboratory confirmed influenza and an influenza-like illness (ILI) during the 2009 pandemic and two prior influenza
seasons. The primary outcome measure was hospital length of stay (LOS). All variables potentially associated with
LOS based on univariable analysis, previous studies, or hypothesized relationships were included in the regression
models to ensure adjustment for their effects.
Results: There were 133 pediatric cases of nH1N1 admitted during 2009 and 133 cases of SI admitted during the
prior 2 influenza seasons (2007-8 and 2008-9). Thirty-six percent of children with SI and 18% of children with
nH1N1 had no preexisting medical conditions (p = 0.14). Children admitted with SI had 1.73 times longer adjusted
LOS than children admitted for nH1N1 (95% CI 1.35 - 2.13). There was a trend towards more children with SI
requiring mechanical ventilation compared with nH1N1 (16 vs.7, p = 0.08).
Conclusions: This study strengthens the growing body of evidence demonstrating that SI results in significant
morbidity in the pediatric population. Pandemic H1N1 received considerable attention with strong media
messages urging people to undergo vaccination and encouraging improved infection control efforts. We believe
that this attention should become an annual effort for SI. Strong unified messages from health care providers and
the media encouraging influenza vaccination will likely prove very useful in averting some of the morbidity related
to influenza for future epidemics.
Background
In April 2009, a novel influenza A H1N1 (nH1N1) virus
emerged and spread rapidly worldwide. News of the
pandemic led to a heightened awareness of the conse-
quences of influenza, as well as some apprehension, in
both the general population, the public health sector,
and among healthcare providers. Concerns regarding
the potential impact of this novel influenza strain led to
enhanced infection control practices and strengthened
vaccination efforts for both healthcare workers and the
general population.”[1-5] The media was actively
involved in informing the public of the potential conse-
quences of influenza infection and encouraging vigorous
vaccination efforts [6].
* Correspondence: ptamma1@jhmi.edu
1
Department of Pediatric Infectious Diseases, The Johns Hopkins Medical
Institution, 200 North Wolfe Street, Suite 3150 Baltimore, Maryland, 21287,
USA
Full list of author information is available at the end of the article
Tamma et al.BMC Pediatrics 2010, 10:72
http://www.biomedcentral.com/1471-2431/10/72
© 2010 Tamma et al ; licensee BioMed Centra l Ltd. This is an Open Access article distri buted under the terms of the Creative Commons
Attribution L icense (http://creati vecommons.org/licenses/by/2.0), which perm its unrestricted use, di stribution, and reproduction in
any medium, provided the original work is properly cited.
Importantly, seasonal influenza (SI) illness in the
pediatric population has been previously shown to result
in significant morbidity, mortality, as well as substantial
hospital resource utilization [7-10]. Although influenza
pandemics have the possibility of resulting in consider-
able illness, we cannot ignore the impact we experience
annually with SI. Perhaps the aggressive campaigning
and resource allocation reserved for pandemic influenza
should be emphasized on an annual basis for SI. We
compared the outcomes of a large cohort of pediatric
patients admitted for nH1N1 infection to children
admitted with SI in the 2007-8 and 2008-9 influenza
seasons to determine if there was a significant difference
in morbidity. We hypothesized that children admitted
with SI would have outcomes including admission to
the pediatric intensive care unit, presence of bacterial
superinfections, and hospital length of stay (LOS) similar
to those admitted with nH1N1.
Methods
Setting
This is a retrospective, cohort study conducted at The
Johns Hopkins Children’s Medical and Surgical Center
(JHCMSC), a part of the Johns Hopkins Hospital (JHH).
The JHCMSC is 175-bed pediatric teaching hospital
located in Baltimore, Maryland that provides medical
care to the Baltimore community and also serves as a
tertiary care pediatric hospital for the surrounding
region. The hospital admits >8500 children annually, of
which >1600 are cared for in the 26-bed pediatric inten-
sive care unit (PICU).
Study Period and Population
We included all children and adolescents 18 years of age
and younger admitted to the JHCMSC with a labora-
tory-confirmed diagnosis of influenza within 24 hours of
admission and an influenza-like illness (ILI). An ILI was
defined as a fever and upper respiratory tract symptoms
(cough, sore throat, rhinorrhea,congestion),lower
respiratory symptoms (wheezing, chest pain, shortness
of breath), or gastrointestinal symptoms (abdominal
pain, vomiting, diarrhea). There were no exclusion cri-
teria. Influenza cases during the 2007-9 seasons that
met the inclusion criteria were evaluated. The nH1N1
cases were compared to SI cases.
The Hospital Epidemiology and Infection Control
(HEIC) Department has an active surveillance program
for respiratory infections among all patients presenting
to JHH. http://www.hopkinsmedicine.org/heic/ID/h1n1/
index.html. All children with ILI admitted to the
JHCMSC are sampled for respiratory viruses. Results are
prospectively recorded into the electronic patient medi-
cal record and simultaneously supplied to the HEIC
computer surveillance system (TheraDoc, Inc, Salt Lake
City, UT). One Infection Control Practitioner (AB)
queries the system prospectively to identify all patients
with positive influenza testing and additional data are
abstracted and included in a database. Pediatric cases
were identified from the master HEIC database. Medical
records were reviewed and demographic, laboratory,
radiographic, and clinical data were collected onto stan-
dardized case report forms. Patients were identified as
having bacterial pneumonia based on previously
described criteria including radiographic evidence of a
new infiltrate [11].
Laboratory Methods
All respiratory virus samples were collected via naso-
pharyngeal aspirate (NPA) by trained nursing staff.
Respiratory virus testing from May-December 2009 con-
sisted of direct fluorescent antibody (DFA) assay (D
3
,
Diagnostic Hybrids Inc.[DHI], Athens, OH). Shell vial
(R-Mix Too, DHI) and conventional tube cultures (rhe-
sus monkey kidney and A549 cells, Diagnostic Hybrids,
Inc.) were inoculated in parallel with DFA for all sam-
ples. Rapid immuno-card tests (BINAX NOW Influenza
A and B, Inverness Medical, Princeton, NJ) were per-
formed initially on all NPA samples from December -
April of 2007-8 and 2008-9. No further testing was per-
formed on positive samples; DFA, shell vial, and tube
culture were performed on all samples with a negative
immuno-card result.
From May through December 2009, all influenza A
positive samples from admitted children were sent to
The Maryland Department of Health and Mental
Hygiene and confirmed by real-time reverse transcrip-
tase-PCR as novel influenza A (H1N1) as described by
the Centers for Disease Control and Prevention (CDC)
[12].
Statistical Analysis
Statistical analyses were performed using Stata version
10.0 (STATA Corp., College Station, TX) and the R sta-
tistical package (version 2.10.1). Comparisons between
patients with seasonal influenza and nH1N1 influenza
were performed using Fisher’s exact test for non-para-
metric data and Student’s t-test with unequal variances
for continuous variables. Hospital LOS was log trans-
formed to achieve a normal distribution and analyzed
using linear regression and Poisson regression models.
Models including interaction terms and excluding high
leverage observations were fitted and residual analysis
including residuals plots, Q-Q plots, and added variable
plots were examined for violations of regression model
assumptions. All variables potentially associated with
LOS based on univariable analysis, previous studies, or
hypothesized relationships were included in the final lin-
ear model to ensure adjustment for their effects. Two-
Tamma et al.BMC Pediatrics 2010, 10:72
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Page 2 of 7
sided p-values of < 0.05were treated as statistically sig-
nificant for all tests. The Johns Hopkins University Insti-
tutional Review Board approved the study with a waiver
of informed consent.
Results
We identified 133 pediatric patients with a laboratory-
confirmed diagnosis of seasonal influenza during the
2007-9 seasons. Coincidentally, we identified 133 chil-
dren with laboratory-confirmed nH1N1 who met our
inclusion criteria. The first confirmed nH1N1 virus
infection at JHCMSC occurred on May 1
st
, 2009 and
the last case included in this study was diagnosed on
November 25
th
, 2009. Figure 1 depicts the epidemic
curve of nH1N1 and seasonal influenza during the prior
two epidemic periods at JHCMSC. Similar proportions
of children with positive laboratory testing for influenza
in the emergency room were admitted to JHCMSC dur-
ing the nH1N1 pandemic and prior influenza seasons
(38% vs. 47%, p = 0.12 ). There was no difference in the
percentage of hospitalized patients admitted directly to
the PICU (19% vs. 18%, p = .99).
We aggregated SI data from the two prior seasons
because patients in the 2007-8 and 2008-9 seasons were
not significantly different in terms of demographic fea-
tures, underlying medical conditions, clinical course, and
outcomes (data not shown). All patients had valid rea-
sons for admission including hypoxia, respiratory dis-
tress, shock requiring pressors, immunocompromised
and febrile, neonates with fever, or sickle cell disease
with fever. These patient types were equally distributed
between the seasons (p ≥0.17).
Demographics and presenting symptoms
Children admitted with SI and nH1N1 influenza were
similar with regards to age, race, and gender (Table 1).
Presenting symptoms were also similar among patients
with SI and nH1N1 influenza infection (Table 1); except
seizures were reported in 19 (14%) of the children with
SI and 5 (4%) of the children with nH1N1 (p = 0.004).
Eleven of the children admitted for SI and 4 of the chil-
dren admitted for nH1N1 who presented with seizures
had no known underlying seizure disorder.
Preexisting Medical Conditions
Thirty-five (26%) children admitted with seasonal influ-
enza and 24 (18%) patients with nH1N1 had no preex-
isting medical conditions (p = 0.14). Twenty (15%) SI
and 40 (30%) nH1N1 admissions had an underlying
diagnosis of asthma (p < 0.01). Neuromuscular disorders
were more prevalent in children admitted with SI com-
pared with nH1N1 (18% vs.7%, p < 0.01). There were
otherwise no significant differences with regards to
underlying medical conditions between the two groups.
(Table 2)
Antimicrobial use
Based on CDC guidelines, and in contrast to SI epi-
demics, antiviral therapy was recommended for all
admitted patients with nH1N1 [5]. Thirty-seven (28%)
Figure 1 Epidemic curve of pandemic influenza A H1N1 and seasonal influenza (2007-2008 and 2008-2009) for children admitted to
The Johns Hopkins Children’s Medical and Surgical Center.
Tamma et al.BMC Pediatrics 2010, 10:72
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children with SI and 106 (80%) children admitted with
nH1N1 received antiviral therapy with activity against
influenza (p < 0.001). When stratifying LOS based on
influenza type and antiviral therapy, LOS was not
modified. (Table 3) Chest imaging was performed on a
significantly higher proportion of children with nH1N1
compared with SI (92% vs. 83%, p = 0.03). However,
similar percentages of children in both groups met
diagnostic criteria for bacterial pneumonia (23% vs.
23%). Interestingly, 61 (72%) of nH1N1 and 37 (36%)
SI children, received treatment courses of antibiotics
for a diagnosis of “bacterial pneumonia”(p < 0.01).
Ten children admitted for SI had bacteremia. Blood
cultures grew methicillin-resistant Staphylococcus aureus
in 3 children, methicillin-susceptible Staphylococcus
aureus in another 3 children, and Streptococcus pneumo-
niae in 3 children. One child grew Streptococcus pyo-
genes in a blood culture. No bacteremia was identified
in any of the children with nH1N1.
Outcomes
The median LOS for SI was 2 days longer than nH1N1; 5
days [IQR 3-7] vs. 3 days [IQR 2-4]. (Table 4) One patient
in the SI cohort had a LOS of 254 days due to complica-
tions unrelated to influenza; however, mean LOS
remained significant after this outlier was removed (p <
0.001). After adjusting for age, race, gender, number of co-
morbid illnesses, presence of a neuromuscular disorder,
asthma, obesity, presence of an infiltrate concerning for
bacterial pneumonia, antiviral therapy, and >48 hours of
antibiotic use, children with SI had 1.73 times longer LOS
(95% CI 1.35 - 2.13) than children with nH1N1.
Thirty-seven (28%) SI cases and 27 (20%) nH1N1
cases (p = 0.20) were admitted to the PICU. Sixteen
(12%) of the SI children required noninvasive positive
pressure ventilation compared with 11(8%) of the
nH1N1 children (p = 0.31). There was a trend towards
more children with SI requiring mechanical ventilation
compared with nH1N1 (16 vs.7, respectively p = 0.08).
One patient, with no underlying medical conditions,
diagnosed with SI required extracorporeal membrane
oxygenation. This patient subsequently died. There were
no deaths in children admitted with nH1N1.
Table 1 Demographic characteristics, presenting
symptoms, and diagnostic testing of children admitted
with seasonal influenza (2007-2009) and 2009 novel
influenza A (nH1N1) infection
Seasonal
influenza
nH1N1
influenza
p-
value
Demographic
characteristics
133 133
Age
Mean (SD) 7.0 (5.7) 7.3 (5.4) .64
Median 5.0 6.0
Race .43
African American 76 (57%) 83 (62%)
Asian 2 (2%) 5 (4%)
Caucasian 47 (35%) 37 (28%)
Hispanic 8 (6%) 8 (6%)
Gender .81
Male 67 (50%) 70 (53%)
Female 66 (50%) 63 (47%)
Presenting Symptoms
†
Upper respiratory tract 110 (83%) 116 (87%) .39
Lower respiratory tract 55 (41%) 61 (46%) .50
Gastrointestinal 35 (26%) 43 (32%) .35
Mylagias 14 (11%) 8 (6%) 27
Headaches 11 (8%) 18 (14%) .24
Seizures 19 (14%) 5 (4%) < .01
Lethargy 33 (25%) 40 (30%) .41
Diagnostic Testing
††
Rapid immuno-card
†††
55 (41.4%) N/A
Direct fluorescent
antibody
78(33%) 39 (29%) .39
Shell vial culture 36 (46%) 90 (68%) .02
Tube culture 16 (21%) 4(3%) .40
†
Fever was part of inclusion criteria,
††
By 1
st
positive test,
†††
If positive for
seasonal influenza no further testing performed
Table 2 Preexisting medical conditions among children
admitted with seasonal influenza (2007-2009) and novel
influenza A H1N1 (nH1N1) infection
Seasonal
influenza
nH1N1
influenza
p-
value
None 35 (26%) 24(18%) .14
Obesity
†
49 (46%) 51(45%) 1.00
Asthma 20 (15%) 40 (30%) < .01
Sickle Cell Disease 17 (12.8%) 26 (20%) .18
Neuromuscular
Disorder
24 (18%) 9 (7%) < .01
Diabetes Mellitus
(type 1)
2 (2%) 2 (2%) 1.00
Chronic Lung Disease 15 (11%) 15 (11%) 1.00
Malignancy 13 (10%) 11(8%) .83
Immunodeficiency
††
10 (8%) 4 (3%) .17
Prematurity (24-37 w) 5 (4%) 10 (8%) .29
Cardiac disorder 8 (6%) 5 (4%) .57
Metabolic disorder 7 (5%) 7 (5%) 1.00
Renal Failure 3 (2%) 1 (1%) .62
Cystic Fibrosis 4 (3%) 3 (2%) 1.00
†
Body mass index ≥90%,
††
HIV, solid organ transplant, immunodeficiency,
corticosteroids ≥2 mg/kg/day for >14 days
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Discussion
It is critical to understand outcomes for infections to
ensure appropriate planning and utilization of healthcare
resources. We compared the clinical outcomes of
nH1N1 to those of SI in a large cohort of hospitalized
children. We found that children admitted with epi-
demic influenza over the past two influenza seasons
(2007-9) appeared to have a longer adjusted LOS, with a
median of almost 2 more days of hospitalization than
children admitted for nH1N1. Median LOS in our popu-
lation of children was somewhat higher than reported in
other retrospective cohort studies and may be related to
the higher percentage of children with high-risk medical
conditions in our cohort compared with other studies
[10,13].
Despite initial concerns about severity of disease
expected for pandemic nH1N1, our data demonstrates
that outcomes among patients with SI are at least as
concerning. This is particularly relevant as there was a
concerted effort to improve infection prevention and
control practices, immunization use, and bed allotment
for the anticipated large numbers of critically ill children
with nH1N1[1-6]. Based on results from our study,
some of these practices may need to be sustained on an
annual basis for SI.
The significance of SI appears to be underappreciated
by the general population and the health care commu-
nity. Although the majority of epidemic influenza virus
infection is usually mild, influenza has the potential to
cause severe disease, particularly in young children and
children with underlying medical conditions [14,15].
Children are disproportionately affected by hospitaliza-
tion rates during SI epidemics. A review of a national
database found that the relative risk (RR) for an influ-
enza-associated hospitalization relative to death was esti-
mated to be 270 for children 5 years of age and under,
compared to 11 amongst adults aged 50-64 [8]. While
mortality is often used to estimate the effect of influenza
among adults, it may be an insensitive indicator of the
effect of influenza in children as the primarily burden is
related to its morbidity [16,17].
Among healthy-children, oseltamivir has been shown
to reduce median duration of influenza illness by 36
hours [18]. Although the decreased LOS with nH1N1
could be attributed to wider antiviral use in this popula-
tion, our data does not support this interpretation. After
Table 3 The timing of antiviral therapy and length of stay among children admitted with seasonal influenza (2007-
2009) and novel H1N1 influenza (nH1N1)
Seasonal influenza
LOS
†
nH1N1 influenza
LOS
†
p-value
No antiviral therapy 7.2 days (n = 92) 3.6 days (n = 27) < .01
Antiviral therapy 6.7 days (n = 37) 4.4 days (n = 106) .03
Antiviral therapy ≥48 hours after symptom onset or no antiviral therapy 7.2 days (n = 120) 4.5 days (n = 82) < .01
Antiviral therapy ≤48 hours of symptom onset 5.6 days (n = 12) 3.7 days (n = 51) .11
†
Median length of stay, (n = number in each sample)
Table 4 Non-pharmacologic treatments and outcomes of children admitted with seasonal influenza (2007-2009) and
novel influenza A H1N1 (nH1N1)
Seasonal influenza nH1N1 influenza p-value
Length of Stay 0.02
Mean (SD) 8.9 (23.0) days 4.2 (4.8) days
Median (Range) 5 (1 - 254) 3 (1 -32)
PICU admission 37 (28%) 27 (20%) 0.20
Need for noninvasive positive pressure ventilation 16 (12%) 11 (8%) 0.31
Need for mechanical ventilation 16 (12%) 7 (5%) 0.08
Days of oxygen 0.14
Mean (SD) 8.7 (19.3) 4.2 (5.3)
Median (Range) 4 (1 -140) 2.5 (1-30)
Days of positive pressure ventilation or mechanical ventilation 0.74
Mean (SD) 7.04 (1.71) 6.14(1.87)
Median (Range) 5(1-38) 2.5 (1-24)
PICU length of stay 0.20
Mean (SD) 10.9 (29.3) days 4.5 (5.7) days
Median (Range) 4 (1- 179) 2 (1 - 26)
Tamma et al.BMC Pediatrics 2010, 10:72
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stratifying by antiviral therapy and influenza type, the
difference in LOS between SI and nH1N1 pediatric
admissions persisted and antiviral therapy did not
appear to significantly influence LOS in our study. Pro-
spective data are needed to define the relative benefits
of early antiviral therapy in hospitalized pediatric
patients.
In both SI and nH1N1 patients in our cohort, antibio-
tics were prescribed for bacterial pneumonia when cri-
teria for this diagnosis were not fulfilled. Almost 50% of
patients with nH1N1 who received antibiotics for a
diagnosis of “bacterial pneumonia”did not meet clinical
criteria. Unnecessary prescription of antibiotics may
have been related to the general apprehension in the
health care community with regards to pandemic
nH1N1. Antibiotics have the potential for associated
toxicities, costs, and the development of multi-drug
resistant organisms. Future studies are needed to better
determine the criteria for antibiotics for influenza-
related bacterial complications.
During the nH1N1 pandemic, there were widespread
media efforts to educate the public about potential conse-
quences of influenza and need for vaccination, especially
for the most high-risk groups. Given that annual influenza
vaccination is the most effective method for preventing
influenza virus infection and its complications, additional
efforts need to be made to ensure annual SI vaccination of
all children, particularly children at higher risk for influ-
enza complications [8,9,14,15,19-22]. Our results empha-
size the need for vaccination against seasonal influenza in
order to reduce its associated morbidity.
There are several limitations of our study. First,
because of the heightened awareness associated with
nH1N1, there is the possibility that the influence of pan-
demic influenza publicity may have lowered the thresh-
old for admission of nH1N1 cases when compared with
SI cases. In our review, all children admitted to the hos-
pital had valid reasons for hospital admission and these
reasons were distributed equally between patients with
nH1N1 and SI. As other measures to determine if the
threshold for hospitalization differed during the pan-
demicperiodascomparedtothepriortwoinfluenza
seasons, we assessed the proportion of hospitalized
patients directly admitted to the PICU and the propor-
tion of children with laboratory-confirmed influenza-like
illness observed in the emergency room admitted to the
hospital. There was no difference in these proportions
further suggesting that these admissions were likely jus-
tified. The proportion of children evaluated in the emer-
gency room and subsequently admitted to the hospital
in our cohort is comparable to what has been previously
reported in the literature for SI [10].
Second, no conclusions can be made regarding the
differences in the virulenceofthestrainsofinfluenza
virus from this paper as we were unable to compare
strain types. Children admitted with SI in the 2007-8
and 2008-9 seasons were not significantly different in
terms of demographic features, underlying medical con-
ditions, clinical course, and outcomes; however, we
recognize that influenza types and subtypes, which vary
from season to season, have differential effects on mor-
bidity and mortality [23-25]. Our results demonstrate
that SI 2007-9 was at least as significant a cause of
pediatric morbidity as nH1N1.
Conclusions
Pandemic nH1N1 received considerable attention with
strong media messages urging people to be vaccinated
and encouraging improved infection control efforts. As
our study strengthens the growing body of evidence
demonstrating that SI results in significant morbidity in
the pediatric population, we believe that the emphasis on
influenza vaccination should be continued on an annual
basis and not solely reserved for influenza pandemics.
List of Abbreviations
All abbreviations are defined in the text where first used.
Acknowledgements
The authors would like to acknowledge the contributions of the nurses and
pediatricians caring for these children, medical microbiology laboratory
technologists, Maria Paz Carlos, PhD, Robert Myers PhD and the staff at
Maryland Department of Health, and the Infection Control Practitioners who
contributed in numerous ways. The authors would also like to acknowledge
Abigail L. Carlson for her contributions to the study.
Author details
1
Department of Pediatric Infectious Diseases, The Johns Hopkins Medical
Institution, 200 North Wolfe Street, Suite 3150 Baltimore, Maryland, 21287,
USA.
2
Department of Epidemiology, Johns Hopkins University Bloomberg
School of Public Health, 615 N. Wolfe Street Baltimore, Maryland, 21287, USA.
3
Department of Infectious Diseases, The Johns Hopkins Medical Institution,
600 North Wolfe Street, Osler 424 Baltimore, Maryland, 21287, USA.
4
Department of Pathology, The Johns Hopkins Medical Institution, Meyer B1-
193, 600 North Wolfe Street Baltimore, Maryland, 21287, USA.
5
Department
of Infection Control, The Johns Hopkins Medical Institution, 600 North Wolfe
Street, Osler 424 Baltimore, Maryland, 21287, USA.
6
Department of Infectious
Diseases, The Johns Hopkins Medical Institution, 600 North Wolfe Street,
Osler 424, Baltimore, Maryland, 21287, USA.
Authors’contributions
PDT performed data collection, analysis, and manuscript preparation. AT
assisted with regression models. AMM and SEC critically reviewed the
manuscript. AV was involved with the laboratory methods and ensured all
nH1N1 strains were confirmed by PCR. AB provided a detailed database of
all influenza positive patients including proportions of those children in the
emergency department subsequently admitted to the hospital. TMP
conceived the idea of the study and was involved in design and manuscript
preparation. All authors read and approved the final draft.
Competing interests
The authors declare that they have no competing interests.
Tamma et al.BMC Pediatrics 2010, 10:72
http://www.biomedcentral.com/1471-2431/10/72
Page 6 of 7
Received: 16 May 2010 Accepted: 6 October 2010
Published: 6 October 2010
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Pre-publication history
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doi:10.1186/1471-2431-10-72
Cite this article as: Tamma et al.: Clinical outcomes of seasonal
influenza and pandemic influenza A (H1N1) in pediatric inpatients. BMC
Pediatrics 2010 10:72.
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