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

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.