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. 2013 Sep;7(5):710-7.
doi: 10.1111/irv.12022. Epub 2012 Dec 5.

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

Eduardo Azziz-Baumgartner  1 , Ana María Cabrera, Po-Yung Cheng, Enio Garcia, Gabriela Kusznierz, Rogelio Calli, Clarisa Baez, María Pía Buyayisqui, Eleonora Poyard, Emanuel Pérez, Ricardo Basurto-Davila, Rakhee Palekar, Otavio Oliva, Airlane Pereira Alencar, Regilo de Souza, Thais dos Santos, David K Shay, Marc-Alain Widdowson, Joseph Breese, Horacio Echenique
Affiliations

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

Eduardo Azziz-Baumgartner et al. Influenza Other Respir Viruses. 2013 Sep.

Abstract

Background: We estimated rates of influenza-associated deaths and hospitalizations in Argentina, a country that recommends annual influenza vaccination for persons at high risk of complications from influenza illness.

Methods: We identified hospitalized persons and deaths in persons diagnosed with pneumonia and influenza (P&I, ICD-10 codes J10-J18) and respiratory and circulatory illness (R&C, codes I00-I99 and J00-J99). We defined the influenza season as the months when the proportion of samples that tested positive for influenza exceeded the annual median. We used hospitalizations and deaths during the influenza off-season to estimate, using linear regression, the number of excess deaths that occurred during the influenza season. To explore whether excess mortality varied by sex and whether people were age <65 or ≥ 65 years, we used Poisson regression of the influenza-associated rates.

Results: During 2002-2009, 2411 P&I and 8527 R&C mean excess deaths occurred annually from May to October. If all of these excess deaths were associated with influenza, the influenza-associated mortality rate was 6/100,000 person-years (95% CI 4-8/100,000 person-years for P&I and 21/100,000 person-years (95% CI 12-31/100,000 person-years) for R&C. During 2005-2008, we identified an average of 7868 P&I excess hospitalizations and 22,994 R&C hospitalizations per year, resulting in an influenza-associated hospitalization rate of 2/10,000 person-years (95% CI 1-3/10,000 person-years) for P&I and 6/10,000 person-years (95% CI 3-8/10,000 person-years) for R&C.

Conclusion: Our findings suggest that annual rates of influenza-associated hospitalizations and death in Argentina were substantial and similar to neighboring Brazil.

Keywords: Argentina; hospitalizations; incidence; influenza; mortality; respiratory.

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Figures

Figure 1
Figure 1
Proportion of clinical respiratory samples tested in Argentina during 2002–2009 which were positive for influenza virus, by month.
Figure 2
Figure 2
Observed, predicted, and excess deaths diagnosed by clinicians with respiratory and circulatorya causes of death during influenza season, Argentina, 2002–2009. aWe assumed the excess respiratory and circulatory events during the influenza season approximate the totality of the annually influenza‐associated mortality. We considered excess deaths (difference between observed and predicted) to be significant only if observed deaths exceeded the upper 95% confidence interval of the predicted deaths.
Figure 3
Figure 3
(A) Rates of influenza‐associated deaths due to respiratory and circulatorya disease and their 95% confidence interval, Argentina, 2002–2009. (B) Rate of influenza‐associated hospitalizations for respiratory and circulatorya causes and their 95% confidence interval, Argentina, 2002–2009. a We assumed the excess respiratory and circulatory events during the influenza season approximate the totality of the annually influenza‐associated mortality.
Figure 4
Figure 4
Number of observed, predicted, and excess respiratory and circulatorya hospitalizations during the influenza season in Argentina, 2005–2008. aWe assumed the excess respiratory and circulatory events during the influenza season approximate the totality of the annually influenza‐associated mortality. We only considered difference between observed and predicted deaths (the excess deaths) to be significant if observed deaths exceeded the upper 95% confidence interval of the model.
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