Estimated global mortality associated with the first 12 months of 2009 pandemic influenza A H1N1 virus circulation: a modelling study.
BACKGROUND
18,500 laboratory-confirmed deaths caused by the 2009 pandemic influenza A H1N1 were reported worldwide for the period April, 2009, to August, 2010. This number is likely to be only a fraction of the true number of the deaths associated with 2009 pandemic influenza A H1N1. We aimed to estimate the global number of deaths during the first 12 months of virus circulation in each country.


METHODS
We calculated crude respiratory mortality rates associated with the 2009 pandemic influenza A H1N1 strain by age (0-17 years, 18-64 years, and >64 years) using the cumulative (12 months) virus-associated symptomatic attack rates from 12 countries and symptomatic case fatality ratios (sCFR) from five high-income countries. To adjust crude mortality rates for differences between countries in risk of death from influenza, we developed a respiratory mortality multiplier equal to the ratio of the median lower respiratory tract infection mortality rate in each WHO region mortality stratum to the median in countries with very low mortality. We calculated cardiovascular disease mortality rates associated with 2009 pandemic influenza A H1N1 infection with the ratio of excess deaths from cardiovascular and respiratory diseases during the pandemic in five countries and multiplied these values by the crude respiratory disease mortality rate associated with the virus. Respiratory and cardiovascular mortality rates associated with 2009 pandemic influenza A H1N1 were multiplied by age to calculate the number of associated deaths.


RESULTS
We estimate that globally there were 201,200 respiratory deaths (range 105,700-395,600) with an additional 83,300 cardiovascular deaths (46,000-179,900) associated with 2009 pandemic influenza A H1N1. 80% of the respiratory and cardiovascular deaths were in people younger than 65 years and 51% occurred in southeast Asia and Africa.


CONCLUSIONS
Our estimate of respiratory and cardiovascular mortality associated with the 2009 pandemic influenza A H1N1 was 15 times higher than reported laboratory-confirmed deaths. Although no estimates of sCFRs were available from Africa and southeast Asia, a disproportionate number of estimated pandemic deaths might have occurred in these regions. Therefore, efforts to prevent influenza need to effectively target these regions in future pandemics.


BACKGROUND
None.
Influenza Division, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA. fdawood@cdc.gov
Fatimah S
FS
Dawood
A Danielle
AD
Iuliano
Carrie
C
Reed
Martin I
MI
Meltzer
David K
DK
Shay
Po-Yung
PY
Cheng
Don
D
Bandaranayake
Robert F
RF
Breiman
W Abdullah
WA
Brooks
Philippe
P
Buchy
Daniel R
DR
Feikin
Karen B
KB
Fowler
Aubree
A
Gordon
Nguyen Tran
NT
Hien
Peter
P
Horby
Q Sue
QS
Huang
Mark A
MA
Katz
Anand
A
Krishnan
Renu
R
Lal
Joel M
JM
Montgomery
Kåre
K
Mølbak
Richard
R
Pebody
Anne M
AM
Presanis
Hugo
H
Razuri
Anneke
A
Steens
Yeny O
YO
Tinoco
Jacco
J
Wallinga
Hongjie
H
Yu
Sirenda
S
Vong
Joseph
J
Bresee
Marc-Alain
MA
Widdowson
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