Mortality, Severe Acute Respiratory Infection, and Influenza-Like Illness Associated with Influenza A(H1N1)pdm09 in Argentina, 2009

Abstract

IntroductionWhile there is much information about the burden of influenza A(H1N1)pdm09 in North America, little data exist on its burden in South America.MethodsDuring April to December 2009, we actively searched for persons with severe acute respiratory infection and influenza-like illness (ILI) in three sentinel cities. A proportion of case-patients provided swabs for influenza testing. We estimated the number of case-patients that would have tested positive for influenza by multiplying the number of untested case-patients by the proportion who tested positive. We estimated rates by dividing the estimated number of case-patients by the census population after adjusting for the proportion of case-patients with missing illness onset information and ILI case-patients who visited physicians multiple times for one illness event.ResultsWe estimated that the influenza A(H1N1)pdm09 mortality rate per 100,000 person-years (py) ranged from 1.5 among persons aged 5–44 years to 5.6 among persons aged ≥65 years. A(H1N1)pdm09 hospitalization rates per 100,000 py ranged between 26.9 among children aged <5 years to 41.8 among persons aged ≥65 years. Influenza A(H1N1)pdm09 ILI rates per 100 py ranged between 1.6 among children aged <5 to 17.1 among persons aged 45–64 years. While 9 (53%) of 17 influenza A(H1N1)pdm09 decedents with available data had obesity and 7 (17%) of 40 had diabetes, less than 4% of surviving influenza A(H1N1)pdm09 case-patients had these pre-existing conditions (p≤0.001).ConclusionInfluenza A(H1N1)pdm09 caused a similar burden of disease in Argentina as in other countries. Such disease burden suggests the potential value of timely influenza vaccinations.

Incidence of influenza‐associated mortality and hospitalizations in Argentina during 2002–2009

“…6,7,17,18 Our findings are similar to those of other studies in Argentina and the Americas and may underscore the value of collecting standardized virology and epidemiology surveillance data. 1,12 For example, our mortality rates are similar to those estimated in Argentina during 1992-1999, 6,7 in neighboring Brazil, 19 and in the United States. 1 Our influenza-associated hospitalization rates during the pandemic are similar to those estimated using a multiplier model from three sentinel cities in Argentina (2.4 (95% CI 2.0-2.8) per 10 000 person-year).…”

Pregnant women infected with pandemic influenza A(H1N1)pdm09 virus showed differential immune response correlated with disease severity

“…During the 2009H1N1 pandemic in Argentina, it was estimated that the mortality rate per 100,000 person-years (py) ranged from 1.5 among persons aged 5-44 years to 5.6 among persons aged ≥65 years [26]. An analysis of 332 case fatalities infected with A(H1N1)pdm09 virus showed that twenty (6%) were among pregnant or postpartum women of whom only 47% had been diagnosed with comorbid disorders [27].…”

Leptin and leptin-related gene polymorphisms, obesity, and influenza A/H1N1 vaccine-induced immune responses in older individuals

“…A recent study has demonstrated that the number of obese persons who were hospitalized with complications of the influenza A/H1N1 infection in 2009 was greater than the number of persons of healthy weight [19]. Moreover, obese individuals had a higher death rate and a greater risk of complications following influenza A infections including A/H1N1 virus infection [23–25]. …”