|
OJHAS Vol. 9, Issue 4:
(Oct-Dec, 2010) |
|
|
| Characteristics of Fatal Cases of Pandemic Influenza
A (H1N1) from September 2009 to January 2010 in Saurashtra Region, India |
|
Rajesh K
Chudasama, Assistant Professor,
Umed V Patel, Associate Professor,
Pramod B
Verma, Professor & Head,
Chikitsa
D Amin, Assistant Professor,
Hitesh M
Shah, Assistant Professor,
Anupam Banerjee,
Assistant Professor,
Ravikant
R Patel, Assistant Professor
Department
of Community Medicine, Government Medical College, Rajkot, Gujarat,
India. |
|
|
| |
|
|
|
|
|
|
Address For Correspondence |
Vandana Embroidary,
Mato Shree Complex,
Sardar Nagar Main Road,
Rajkot – 360 001,
Gujarat, India.
E-mail:
dranakonda@yahoo.com |
|
|
|
|
|
Chudasama RK, Patel UV, Verma PB, Amin CD, Shah HM, Banerjee A,
Patel RR. Characteristics of Fatal Cases of Pandemic Influenza
A (H1N1) from September 2009 to January 2010 in Saurashtra Region, India. Online J Health Allied Scs.
2010;9(4):9 |
|
|
|
|
Submitted: Oct 13,
2010; Accepted: Nov 3, 2010; Published: Jan 20, 2011 |
|
|
|
|
|
|
|
| |
|
| Abstract: |
|
Background: India reported
first case of 2009 pandemic influenza A (H1N1) virus infection in May,
2009 and Saurashtra region in August, 2009. We describe the characteristics
of fatal cases of 2009 influenza A (H1N1) infection reported in Saurashtra
region. Methods: From September,
2009 to January, 2010, we observed 71 fatal cases that were infected
with 2009 influenza A (H1N1) virus and admitted in different hospitals
in Rajkot city. Real-time reverse-transcriptase-polymerase-chain-reaction
(RT-PCR) testing was used to confirm infection; the clinico-epidemiological
features were observed and documented. Results: Median age
of the deceased (71) was 29 years, and 57.7% were females. Median time
observed was 5 days from onset of illness to diagnosis of influenza
A (H1N1), and 57.7% were referred from general practitioner (OR=0.42,
CI=0.24-0.74). Median hospital stay reported was 3 days. All admitted
patients received oseltamivir, but only 16.9% received it within 2 days
of onset of illness. The most common symptoms were cough (97.2%), fever
(93%), sore throat and shortness of breath. Co-morbid conditions were
present in almost half of the patients who ultimately died, the most
common of which was pregnancy (OR=0.15, CI=0.04-0.52). Radiological
pneumonia was reported in 98% patients. Conclusion: Residing in
urban area, delayed referral from general practitioner, presence of
co-existing condition, especially pregnancy was responsible for mortality
among influenza A (H1N1) infected positive.
Key Words:
Influenza A
(H1N1); Epidemiology; Fatal cases; RT-PCR; Pregnancy; Antiviral drug
|
|
The first human
cases of infection with the 2009 pandemic influenza A (H1N1) virus were
confirmed in the Southwest United States in April 2009, although an
epidemic later confirmed to be caused by H1N1 (2009) had been occurring
in Mexico in the weeks prior to detection.1,2 The novel
pandemic influenza A (H1N1) virus was later confirmed to be a triple reassortant virus containing gene segments from swine, avian and human
influenza A virus.1,3,4 On June 11, 2009 the World Health
Organization (WHO) raised the pandemic level from 5 to 6, highest level
after the documentation of human to human transmission of the virus
in at least three countries in two of the six world regions defined
by the WHO.5,6 Similarities with regards to the characteristics
of the influenza A (H1N1) virus have been observed among populations
of both the northern and southern hemispheres.7-10 Further
similarities have been observed globally in the risk factors contributing
to severe disease and death, with underlying disease recorded in at
least half of the fatal cases 11, mainly pregnancy and metabolic
diseases.11,12
Although much
has been published on the characteristics of pandemic influenza A (H1N1)
infection globally7-12, little published data are available
from the Indian subcontinent. The characteristics of pandemic influenza
may differ from other developed countries reporting the infection, considering
the high prevalence of other infectious diseases and significant burden
of non communicable conditions.
The first case
of confirmed pandemic H1N1 infection in India was documented during
May, 2009.13 Incidence rate remained low until August, 2009
when large numbers of cases were reported throughout India. Saurashtra
region which is the western-most part of Gujarat state in India, reported
its first H1N1 positive case during August, 2009. The purpose of this
manuscript is to describe the characteristics of reported pandemic H1N1-related
deaths, from 1st September, 2009 to 31st January,
2010.
The Ministry
of Health and Family Welfare, Government of India, started preparations
for the management of infected patients as soon as the first case was
reported in May, 2009. Gujarat state (including Saurashtra Region) participated
in active surveillance for pandemic H1N1 as of August 2009. Hospitals
having an advanced life saving support were involved in admitting and
managing influenza A (H1N1) positive patients in Rajkot.
Clinical
case /suspected case definition6: A suspected case was
defined as an influenza-like illness (temperature > 37.5˚C
and at least one of the following symptoms: sore throat, cough, rhinorrhea,
or nasal congestion) and either a history of travel to a country where
infection had been reported in the previous 7 days or an epidemiologic
link to a person with confirmed or suspected infection in the previous
7 days. A confirmed case was defined by a positive result of a real-time
reverse transcriptase polymerase chain reaction (RT-PCR).
Variables:
Several types of data collected from the patients include: demographic
information, any coexisting conditions, regarding onset of illness and
treatment taken. Data regarding hospitalization, whether intensive care
was needed, duration of antiviral drug administration, and disease outcome
were collected from medical record and statistics departments of various
hospitals.
Data Management:
All expired patients’ admission history and their medical records
including certified cause of death were assessed for clinico-epidemiological
details. Approval by institutional review board was not required because
of this infectious disease was covered under epidemic act and the state
health department14 had implemented Epidemic Disease Control
Act, 1897 from 18th August, 2009 and issued a notification
that it was in the interest of the public health to collect data on
an emerging pathogen.
Laboratory
confirmation of infection: The 2009 H1N1 virus was detected with
the use of a real time RT-PCR assay in accordance with the protocol
from the US centers for Disease Control and Prevention, as recommended
by the WHO.15 Two swabs from naso-pharynx and one from pharynx
were collected from suspected patients and their contacts for detection
of influenza A (H1N1) virus by real-time RT-PCR assay.
Statistical
analysis: All data was entered in MS Excel, and analyzed by using Epi Info software (version 3.5.1) from CDC.16
Certification
of cause of death: In India, all deaths are recorded on a standard
death certificate, which distinguishes between direct causality (Part
I) and contributory factors (Part II). Part I of the certificate records
diseases or conditions directly leading to death and part II records
conditions contributing to the death but not related to the disease
or condition causing it. Death certificates were also analyzed according
to the methods of ICD-10 (international classification of diseases,
10th revision) 17, used nationally and internationally
to produce national mortality statistics.18
Total 274 patients
were found positive (Figure 1) and admitted in different hospitals of Rajkot from 1st September, 2009 to 31st January,
2010. Out of them, 71 patients who expired were included for analysis.
 |
|
Figure 1:
Age group wise distribution of influenza A (H1N1) positive total (n=274)
and expired (n=71) patients in Saurashtra region from September, 2009
to February, 2010 |
Admission rate
and mortality was highest among below five years (16.9%) children, and
25-45 years (40.8%) age group. Median age of 29 years (Table 1) was
reported among expired patients (range 4 months to 68 years). Significant
number of deaths were occurred in patients residing in urban areas then
in rural areas (OR= 1.95, CI=1.15-3.41). But no such association was
found for male / female. No fatal case reported to have recent
travel history to infected region. Median time, from onset of illness
to diagnosis of influenza A (H1N1), was 5 days. More than half (57.7%)
of fatal cases were treated first at general practitioner and then referred
to higher center for further investigation. Seventeen percent patients
who expired had received antiviral treatment within 2 days of onset
of illness. 87.1% deaths occurred 5 days after onset of illness.
|
Table 1:
Baseline characteristics and disease history of 2009 pandemic influenza
A (H1N1) virus infected patients in Saurashtra region (September, 2009
to January, 2010) |
|
Characteristics |
Non fatal cases (n=203) No. (%) |
Fatal cases (n=71) No.
(%) |
|
Age
in year |
|
Median – year |
27 |
29 |
|
Range |
4 mths-68 yrs |
4 mths-68 yrs |
|
Age
group of positive expired patients – no. (%) |
| < 5 yrs |
27 (13.3) |
12 (16.9) |
|
5-24 yrs |
50 (24.6) |
14 (19.7) |
|
25-44 yrs |
77 (37.9) |
29 (40.8) |
|
45-64 yrs |
45 (22.2) |
14 (19.7) |
|
> 65 yrs |
4 (2.0) |
2 (2.8) |
|
Sex
– no. (%) |
|
Male |
111 (54.7) |
30 (42.3) |
|
Female |
92 (45.3) |
41 (57.7) |
|
Residential
status† – no. (%) |
|
Urban |
143 (70.4) |
39 (54.9) |
|
Rural |
60 (29.6) |
32 (45.1) |
|
Hospital
stays in days – no. (%) |
|
Median (in days) |
5 |
3 |
|
<2 days |
14 (6.9) |
27 (38.0) |
|
3-5 days |
51 (25.1) |
21 (29.6) |
|
6-10 days |
100 (49.3) |
15 (21.1) |
|
>11 days |
38 (18.7) |
8 (11.3) |
|
Time
interval from onset of illness to hospital admission & diagnosis-no.
(%) |
|
Median (in days) |
5 |
5 |
|
<1 day |
12 (5.9) |
6 (8.5) |
|
1-4 days |
91 (44.8) |
24 (33.8) |
|
5-10 days |
89 (43.8) |
40 (56.3) |
|
>10 days |
11 (5.4) |
1 (1.4) |
|
Referral
from general practitioner/physician‡ – no. (%) |
75 (36.9) |
41 (57.7) |
|
Antiviral
treatment – no. (%) |
|
Any antiviral drug received |
203 (100) |
71 (100) |
|
<2 days after onset of symptoms |
32 (15.8) |
12 (16.9) |
|
Time
interval from onset of illness to death – no. (%) |
|
<1 day |
NA§ |
1 (1.4) |
|
1-4 days |
8 (11.3) |
|
5-10 days |
38 (53.5) |
|
>10 days |
24 (33.8) |
|
*An infected
region was defined as an area where one or more confirmed cases of 2009
pandemic influenza A (H1N1) virus infection had been found in the preceding
7 days.
† p<0.01,
Odds Ratio (OR) = 1.95, Confidence Interval (CI) = 1.12-3.41
‡ p<0.01,
OR = 0.42, CI = 0.24-0.74
§ NA- Not
Applicable
|
Cough (97.2%),
fever (93%), shortness of breathing (57.7%), and sore throat (52.1%)
reported mainly among deaths due to influenza A (H1N1) (Table 2).
|
Table 2:
Clinical features and coexisting conditions of patients infected with
influenza A (H1N1) at the time of hospital admission |
|
Characteristics |
Non fatal cases (n=203)
No. (%) |
Fatal cases (n=71)
No.
(%) |
|
Clinical
Features – no. (%) |
|
Cough |
196 (96.6) |
69 (97.2) |
|
Fever (>37.5˚ Celsius) |
186 (91.6) |
66 (93.0) |
|
Shortness/difficulty in
breathing |
105 (51.7) |
41 (57.7) |
|
Sore Throat |
112 (55.2) |
37 (52.1) |
|
Nasal Catarrh |
40 (19.7) |
16 (22.5) |
|
Headache |
52 (25.6) |
19 (26.8) |
|
Vomiting |
13 (6.4) |
14 (19.7) |
|
Coexisting
conditions – no. (%) |
|
Any one condition* |
58 (28.6) |
32 (45.1) |
|
Pregnancy† |
5 (2.5) |
10 (14.1) |
|
Diabetes Mellitus |
22 (10.8) |
5 (7.0) |
|
Hypertension |
19 (9.4) |
5 (7.0) |
|
Chronic Heart Diseases
|
9 (4.4) |
4 (5.6) |
|
Chronic Pulmonary Diseases
|
13 (6.4) |
2 (2.8) |
|
Seizure disorder |
5 (2.5) |
2 (2.8) |
|
*P<0.01; † p<0.01,
OR=0.15, CI=0.04-0.52
|
Little less
than half (45.1%) deaths were reported having coexisting conditions,
including 14.1% pregnant women. Significant association was found between
pregnancy (p=0.01) and influenza A (H1N1) infection among fatal cases.
Laboratory findings (Table 3) like, leukopenia (31%), anemia (44.8%),
lymphopenia, thrombocytopenia (32.1%), elevated alanine aminotransferase
(90.3%), aspartate aminotransferase (37.9%), pneumonia (98.3%) were
reported among fatal cases.
|
Table 3:
Laboratory and radiographic findings on hospital admission in influenza
A (H1N1) infected expired patients in Saurashtra region* |
| Characteristic |
No. /Total No. (%) |
|
Leukocyte
count |
|
Mean count |
7905
± 7566 |
| Leukopenia ( <4,000/ mm3) |
18/58 (31.0) |
| Leukocytosis (>10,000/ mm3) |
14/58 (24.1) |
| Hemoglobin
gm/dl |
11.03
± 2.65 |
|
Anemia
|
|
Mild (10.0-11.0 gm/dl) |
8/58 (13.8) |
|
Moderate (8-10 gm/dl) |
10/58 (17.2) |
|
Severe (<8 gm/dl) |
8/58 (13.8) |
|
Lymphocyte
count |
| <1500/ mm3 in adults |
30/39 (76.9) |
| <3000/ mm3 in children |
2/10 (20.0) |
|
Platelet
count |
|
Mean count |
212, 566
± 151, 843 |
| Thrombocytopenia (<150,000/ mm3) |
17/53 (32.1) |
| Thrombocytosis (>350,000/ mm3) |
6/53 (11.3) |
|
Elevated
alanine aminotransferase (>40 U/liter) |
|
Any deviation |
28/31 (90.3) |
|
≥2× the upper limit of normal range |
27/31 (87.1) |
|
Elevated
aspartate aminotransferase (>40 U/liter) |
|
Any deviation |
11/29 (37.9) |
|
≥2× the upper limit of normal range |
2/29 (6.9) |
| Elevated
total bilirubin (>1.2 mg/dl) |
9/35 (25.7) |
|
Erythrocyte
sedimentation rate |
|
>15 mm/hr in male patients |
8/21 (38.1) |
|
>20 mm/hr in female patients |
6/21 (28.6) |
|
Chest
X-ray findings |
|
Done |
59/71 (83.1) |
|
Pneumonia found |
58/59 (98.3) |
| Antibiotic
treatment received |
64/71 (90.1) |
| Corticosteroid
treatment received |
41/71 (57.7) |
|
* ±
values are mean ± SD. |
Chest radiography
was done in 59 (83.1%) of 71 fatal cases and among them 98.3% reported
bilateral pneumonia. Among all reported deaths, the underlying cause
of death was classified as influenza A (H1N1) in the causal chain directly
leading to death (Table 4).
|
Table 4:
Certification of direct causes of death in expired influenza A (H1N1)
patients in Saurashtra region |
|
Certified
causes of death |
Direct Cause (n=71) No. (%) |
|
Direct
cause (Part I) |
|
Influenza A (H1N1) |
71 (100) |
|
Contributing
cause (Part II) |
|
Pneumonia |
3 (4.2) |
| Acute Respiratory Distress Syndrome (ARDS) |
5 (7.0) |
| Pneumonia and ARDS |
55 (77.5) |
|
Other respiratory complications |
3 (4.2) |
|
Multi organ failure |
6 (8.5) |
| Pre-existing disease (DM, Thalessemia, CHD, RHD) |
5 (7.0) |
During the
previous pandemics of 20th century and during seasonal influenza,
most cases involve transient illness, not requiring hospitalization.
Deaths were described mainly in young adult population or those with
underlying disease.19 Seasonal influenza caused significant
morbidity and mortality throughout the world.20 Present
study identified all patients with confirmed 2009 influenza A (H1N1)
belonging to category C 21, who were hospitalized in various
hospitals in Rajkot from September, 2009 to January, 2010. Category
C includes patients having high grade fever, severe sore throat, any
co-existing condition, breathlessness, chest pain, drowsiness, fall
in blood pressure, sputum mixed with blood, and they were hospitalized
immediately.
Total 274 patients
were hospitalized during study period and among them 71 patients expired.
The majority of expired patients (63%) belonged to age group 25-65 years,
suggesting high fatality rate among adults. The median age of fatal
cases was 29 years, which is lower than that reported in South Africa
(33.5 years)11 and in France (37 years).22 Significant
number of deaths were occurred in patients residing in urban areas then
in rural areas (OR= 1.95, CI=1.15-3.41). But no such association was
found for male / female sex among fatal and non fatal cases. Large number
of people resides in congested areas with poor environmental and hygienic
conditions may be the reason for spread of influenza A (H1N1) virus
in urban area than rural area. Most ultimately fatal cases (57.7%) were
first treated at a general practitioner and then referred to the higher
center (OR=0.42, CI=0.24-0.74). The median time between onset of illness
and hospital admission and diagnosis was more in this study than studies
of other countries.23,24 The possible justification is
that patients seek treatment at local level from general practitioners
and physicians, but with no or little improvement after initial treatment,
they were referred to higher center for further investigation and management.
The vast majority
of 2009 H1N1 viruses that have been tested at the CDC to date have been
susceptible to two neuraminidase inhibitors, oseltamivir and zanamivir,
and resistant to two adamantanes; amantadine and rimantadine.4,25 Current interim CDC guidelines for pandemic and seasonal
influenza recommend the use of either oseltamivir or zanamivir for hospitalized
patients with suspected or confirmed influenza and for outpatients at
high risk for complications.26 Ministry of Health &
Family Welfare, Government of India has recommended and supplied oseltamivir
to the state governments for distribution in tertiary care centers and
district hospitals in adequate quantity. Although the evidence of benefit
from antiviral therapy was strongest when treatment is initiated within
48 hours after the onset of illness, a study with oseltamivir in hospitalized
patients reported reduction in mortality even after 48 hours of onset
of illness.27 In present study, all the influenza A (H1N1)
infected fatal cases received oseltamivir after hospitalization, but
only 16.9% received it within 48 hours of onset of illness, compared
to 45% in United States.23 Initial treatment by general
practitioners and delayed referral to higher center, may be possible
explanations for late start of oseltamivir in suspected or confirmed
influenza A (H1N1) patients.
Fatal cases,
on hospitalization, mainly presented with cough (97.2%), fever (93%),
shortness of breathing (57.7%), and sore throat (52.1%). These observations
are similar to studies done by others in US 23, Australia
and New Zealand.24 In the present study, the proportion
of fatal cases who had at least one coexisting condition was 45%, which
was 36% in England28, and 53% in France.22 Pregnancy
is a well documented risk factor for severe infection and death in seasonal
influenza and in previous pandemics.29-31 In this study,
14.1% of fatal cases were pregnant compared to 2.5% in non-fatal cases
(OR=0.15, CI=0.04-0.52). Out of 10 fatal pregnant cases, 2 were in second
trimester and 8 in third trimesters.
Our study has
a number of strengths. It represents one of the largest series of fatal
cases with severe 2009 influenza A (H1N1) infection covering two seasons
of monsoon and winter. It includes both adults and children from geographically
similar areas, which improves the generalizability of our results to
other regions. These characteristics of risk factors, typical clinical
features, response to therapy, and prognosis should aid in the recognition,
diagnosis and clinical management of influenza A (H1N1).
Our study also
has some limitations. The data was taken only from hospitalized fatal
cases, so patients who became infected, remained undiagnosed, died in
the community and did not go to the hospital were not included in our
study. All diagnostic testing was clinically driven, and other investigations
were not obtained in a standardized fashion. Though we used a standardized
data collection form, we still could not collect all information for
all the patients. The findings may be different during future waves,
owing to timely deployment of an effective vaccine, viral mutation,
and resistance to antiviral drugs.
We have demonstrated
the characteristics of fatal cases of 2009 influenza A (H1N1). Residing
in urban area, delayed referral from general practitioner, presence
of co-existing condition, especially pregnancy was responsible for mortality
among influenza A (H1N1) infected positive.
- Novel swine origin
influenza A (H1N1) virus investigation team. Emergence of a novel swine
origin influenza A (H1N1) virus in humans. N Engl J Med 2009;360:2605-2615.
- Centers for Disease
Control and Prevention (CDC). Swine influenza A (H1N1) infection in
two children-Southern California, March-April 2009. MMWR 2009;58:400-402.
- Ministry of Health
& Family Welfare, Government of India. Factsheet Influenza A (H1N1).
Available from:
http://pib.nic.in/h1n1/factsheet.pdf. Accessed on March
06, 2010.
- Garten RJ, Davis
CT, Russell CA, Shu B, Lindstrom S, Balish A, et al. Antigenic and genetic
characteristics of swine origin 2009 A (H1N1) influenza viruses circulating
in humans. Science 2009;325:197-201.
- World Health Organization.
Influenza A (H1N1) – update 14. Geneva. 2009. Available from:
http://www.who.int/csr/don/2009_05_04a/en/index.html.
Accessed on February 27,
2010.
- Human swine influenza:
a pandemic threat. Director General of Health Services. Government of
India. CD Alert 2009;12:1-8.
- Baker MG, Wilson
N, Huang QS, Paine S, Lopez L, Bandaranayake D, et al. Pandemic influenza
A (H1N1) in New Zealand: the experience from April to August, 2009.
Euro Surveill 2009;14:pii=19319. Available from:
http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=19319. Accessed on January 21, 2010.
- Munayco CV, Gomez
J, Laguna-Torres VA, Arrasco J, Kochel TJ, Fiestas V, et al. Epidemiological
and transmissibility analysis of influenza A (H1N1) in a southern hemisphere
setting: Peru. Euro Surveill 2009;14:pii=19299. Available from:
http://www.eurosuveillance.org/ViewArticle.aspx?ArticleId=19299. Accessed on January 21, 2010.
- de Silva UC, Warachit
J, Waicharoen S, Chittaganpitch M. A preliminary analysis of the epidemiology
of influenza A (H1N1) virus infection in Thailand from early outbreak
data, June-July 2009. Euro Surveill 2009;14:pii=19292. Available from:
http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=19292. Accessed on January 23, 2010.
- Tulloch F, Correa
R, Guerrero G, Samaniego R, Garcia M, Pascale JM, et al. Profile of the first
cases hospitalized due to influenza A (H1N1) 2009 in Panama City, Panama. J Infect Dev Ctries
May-June 2009;3:811-816.
- Archer BN, Cohen
C, Naidoo D, Thomas J, Makunga C, Blumberg L, et al. Interim report
on pandemic H1N1 influenza virus infections in South Africa, April to
October 2009: epidemiology and factors associated with fatal cases.
Euro Surveill 2009;14:pii=19369. Available from:
http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=19369. Accessed on March 12, 2010.
- Belgian working
group on influenza A (H1N1). Influenza A (H1N1) infection in Belgium,
May-June 2009. Euro Surveill 2009;14:pii=19270. Available from:
http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=19270. Accessed on January 14, 2010.
- Ministry of Health
& Family welfare, Government of India. Situation update on H1N1.
2010. Available from:
http://mohfw-h1n1.nic.in/documents/PDF/EpidemiologicalTrendsInIndia.pdf.
Accessed on February 15,
2010.
- Ministry of Health
& Family Welfare, Government of Gujarat. Epidemic Disease Control
Act, 1897. Available from:
http://www.expressindia.com/latest-news/epidemic-control-act-invoked-to-thwart-h1n1-scare-in-state/504144/. Accessed on March 03, 2010.
- World Health Organization.
CDC protocol of realtime RTPCR for swine influenza A (H1N1). Geneva.
April 28, 2009. Available from:
http://www.who.int/csr/resources/publications/swineflu/CDCrealtimeRTPCRprotocol_20090428.pdf.
Accessed on January 15,
2010.
- Centers for Disease
Control & Prevention. Epi Info version 3.5.1, 2008. Available from:
www.cdc.gov/epiinfo/. Accessed on August 15, 2008.
- World Health Organization.
International classification of diseases and related health problems,
10th rev. WHO, 1992.
- Mathers D, Ma Fat
D, Inoue M, Rao C, Lopez AD. Counting the dead and what they died from:
an assessment of the global status of cause of death data. Bull World
Health Organ 2005;83:171-177.
- The European scientific
working group on influenza (ESWI). Pandemics of the 20th
century, 2009. Available from:
http://www.flucentre.org/files/Pandemics%20of%20the%2020th%20century.pdf. Accessed on January 25, 2010.
- World Health Organization.
Influenza (seasonal) factsheet. April, 2009. Available from:
http://www.who.int/mediacentre/factsheets/fs211/en/. Accessed on February 02, 2010.
- Ministry of Health
& Family Welfare, Government of India. Guidelines on categorization
of influenza A H1N1. May, 2009. Available from:
http://mohfw-h1n1.nic.in/documents/pdf/3.Categorization%20of%20Influenza%20A%20H1N1%20cases%20screening.pdf. Accessed on January 15, 2010.
- Vaillant L, La
Ruche G, Tarantola A, Barboza P. Epidemiology of fatal cases associated
with pandemic H1N1 influenza 2009. Euro Surveill 2009;14:pii=19309.
Available from:
http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=19309. Accessed on January 19, 2010.
- Jain S, Schmitz
AM, Louie J, Druckenmiller JK, Chugh R, Deutscher M, et al. Hospitalized
patients with 2009 H1N1 influenza in the United States, April-June 2009.
N Engl J Med 2009;361:1935-1944.
- The ANZIC influenza
investigators. Critical care services and 2009 H1N1 influenza in Australia
and New Zealand. N Engl J Med 2009;361:1925-1934.
- Centers for Disease
Control & Prevention. FluView: a weekly influenza surveillance
report prepared by the Influenza Division. Atlanta. Available from:
http://www.cdc.gov/flu/weekly/. Accessed on January 21, 2010.
- Centers for Disease
Control & Prevention. Updated interim recommendations for the use
of antiviral medications in the treatment and prevention of influenza
for the 2009-2010 seasons. Atlanta. Available from:
http://www.cdc.gov/h1n1flu/recommendations.htm.
Accessed on January 24,
2010.
- McGeer A, Green
KA, Plevneshi A, Shigayeva A, Siddiqi N, Raboud J et al. Antiviral
therapy and outcomes of influenza requiring hospitalization in Ontario,
Canada. Clin Infect Dis 2007;45:1568-1575.
- Donaldson LJ, Rutter
PD, Ellis BM, Greaves FEC, Mytton OT, Pebody RG et al. Mortality from
pandemic A/H1N1 2009 influenza in England: public health surveillance
study. BMJ 2009;339:b5213. doi:10.1136/bmj.b5213.
- Jamieson DJ, Honein
MA, Rasmussen SA, Williams JL, Swerdlow DL, Biggerstaff MS et
al. H1N1 2009 influenza virus infection during pregnancy in the USA.
Lancet 2009;374:451-458.
- Dodds L, McNeil
SA, Fell DB, Allen VM, Coombs A, Scott J et al. Impact of influenza
exposure on rates of hospital admissions and physician visits because
of respiratory illness among pregnant women. CMAJ 2007;176:463-468.
- Neuzil KM, Reed
GW, Mitchel EF, Simonsen L, Griffin MR. Impact of influenza on acute
cardiopulmonary hospitalizations in pregnant women. Am J Epidemiol 1998;148:1094-1102.
|
