Quantifying the mortality caused by the H1N1 influenza virus during the 2009 pandemic in Mexico.

Eusebio Perez-Flores,Juan Carlos Izquierdo-Puente,Gustavo Ramírez-Rosales,Concepción Grajales-Muñiz,Israel Grijalva-Otero,Jose Juan Castillo-Perez,Roman Alejandro Garcia-Ramirez,Juan Manuel Mejia-Arangure,Constantino Lopez-Macias

doi:10.3855/jidc.3622

Eusebio Perez-Flores, Juan Carlos Izquierdo-Puente + Show 7 more

Open Access

https://doi.org/10.3855/jidc.3622

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Abstract

The frequency and mortality of the pandemic caused by influenza A(H1N1)pdm09 might have been underestimated, especially in developing countries. This study was designed to quantify the possible underestimation of pandemic influenza mortality and evaluate the concordance between the data reported for A(H1N1)pdm09 mortality and the causes of death reported during the pandemic period of April 2009 to February 2010. The death certificates of 754 confirmed cases of A(H1N1)pdm09 infection were included in the study. Data was analyzed using the United States Centers for Disease Control and Prevention's statistical model accounts for the variability in the proportion at each step using the Monte Carlo probabilistic model sampled from a uniform probability distribution. A total of 1,969 deaths were estimated, with an estimated lethality of 5.53 per 100,000 (range, 3.5-8.76 per 100,000) in contrast with the 754 deaths and a lethality of 1.98 per 100,000 infected patients officially reported. In 631 of 754 (83.7%) death certificates from A(H1N1)pdm09 influenza-positive patients, influenza was not mentioned as a cause of death. It is possible that the mortality of the pandemic was three times higher than officially reported in Mexico. One source of error that could explain this underestimation is in the completion of death certificates, because in > 80% of confirmed cases of infection with influenza virus, it was not reported as the cause of death.

Highlights

IntroductionInfluenza infections cause substantial mortality and morbidity every year, and estimates of this burden have played a pivotal role in formulating influenza vaccination policies [1]
The frequency and mortality of the pandemic caused by influenza A(H1N1)pdm09 might have been underestimated, especially in developing countries
This work had two main objectives: first, to quantify the possible underestimation of the pandemic influenza mortality between April 2009 and February 2010; and second, to evaluate the relationship between the data reported for A(H1N1)pdm09 mortality during the pandemic period of April 2009 to February 2010 and the causes of death reported on the death certificates of patients infected by the virus

Summary

Introduction

Influenza infections cause substantial mortality and morbidity every year, and estimates of this burden have played a pivotal role in formulating influenza vaccination policies [1]. This work had two main objectives: first, to quantify the possible underestimation of the pandemic influenza mortality between April 2009 and February 2010; and second, to evaluate the relationship between the data reported for A(H1N1)pdm mortality during the pandemic period of April 2009 to February 2010 and the causes of death reported on the death certificates of patients infected by the virus. These data should contribute further to the analysis of the response of the IMSS health care services during the pandemic emergency. This study was approved by the Ethics Board of the National Commission of Scientific Investigation (Registry No 2010-785-019)

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