Mortality Associated with Influenza in Tropics, State of São Paulo, Brazil, from 2002 to 2011: The Pre-Pandemic, Pandemic, and Post-Pandemic Periods

Abstract

The impact of the seasonal influenza and 2009 AH1N1 pandemic influenza on mortality is not yet completely understood, particularly in tropical and subtropical countries. The trends of influenza related mortality rate in different age groups and different outcomes on a area in tropical and subtropical climate with more than 41 million people (State of São Paulo, Brazil), were studied from 2002 to 2011 were studied. Serfling-type regression analysis was performed using weekly mortality registries and virological data obtained from sentinel surveillance. The prepandemic years presented a well-defined seasonality during winter and a clear relationship between activity of AH3N2 and increase of mortality in all ages, especially in individuals older than 60 years. The mortality due to pneumonia and influenza and respiratory causes associated with 2009 pandemic influenza in the age groups 0–4 years and older than 60 was lower than the previous years. Among people aged 5–19 and 20–59 years the mortality was 2.6 and 4.4 times higher than that in previous periods, respectively. The mortality in all ages was higher than the average of the previous years but was equal mortality in epidemics of AH3N2. The 2009 pandemic influenza mortality showed significant differences compared to other years, especially considering the age groups most affected.

Estimating the burden of influenza‐associated hospitalizations and deaths in Central America

“…Our estimated influenza‐associated in‐hospital mortality was similar to that reported previously in the region, except for the lower mortality rates we estimated among adults aged >64 years 6, 12, 13. Our rates among children aged <5 years were also lower than those of a global meta‐analysis using different methodology,1 whereby 4·9 children per 100 000 died from influenza‐associated severe acute lower respiratory infection (ALRI) in developing countries.…”

Deaths Associated with Respiratory Syncytial and Influenza Viruses among Persons ≥5 Years of Age in HIV-Prevalent Area, South Africa, 1998–20091

“…However, pandemic-related mortality rates were higher in the 5-19-year age group and lower in the >45-year age group compared with typical seasons. Other studies have reported overall lower mortality rates associated with the first year of circulation of the 2009 pandemic virus, compared with that of seasonal influenza, but have found a higher disease burden for children and young adults (4,(21)(22)(23)(24)(25). Our estimates are similar to the lower-bound estimates for South Africa from a global influenza A(H1N1)pdm09 mortality model (26).…”

Estimating the burden of influenza‐associated hospitalizations and deaths in Chile during 2012‐2014

“…Furthermore, a higher percent positivity for influenza was reported among the older age‐group as compared to the younger age‐groups, which provides further evidence of the greater burden in this age‐group. This pattern is maintained for all viral subtypes; however, the differences tend to decrease with influenza A(H1N1) perhaps due to the published finding that influenza(H1N1)pdm09 affects younger adults more than older ones due to absence of immune‐protection against this virus (USA, Mexico, Brazil, four European countries) 24, 25, 26…”

“…This pattern is maintained for all viral subtypes; however, the differences tend to decrease with influenza A(H1N1) perhaps due to the published finding that influenza(H1N1)pdm09 affects younger adults more than older ones due to absence of immune-protection against this virus (USA, Mexico, Brazil, four European countries). [24][25][26] Our estimates for persons aged 65 years and older are greater than those reported in an analysis from Central America using the (170-1033 influenza-associated hospitalizations per 100 000 persons-years). 17 Our estimates found among children under 5 years of age are similar to the global meta-analysis for countries in the Americas (71 influenza-associated hospitalizations per 100 000 persons-years) 27 and lower than the estimates from Central American countries (113 influenza-associated hospitalization per 100 000 persons-year).…”