Seroprevalence study of infection with influenza A(H1N1)pdm09 virus in San Felipe Town, Chile

Olea Andrea, Fasce Rodrigo, Aguilera Ximena, Oliva Otavio, Muñoz Sergio, García Maritza, Pedroni Elena, Nájera Manuel, Guerrero Andrea, Bustos Patricia, Mora Judith, Vega Jeanette, Cerda Jaime, Abarca Katia, McCarron Meg, Widdowson Marc-Alain, Castillo Ernesto, Alvarado Sergio, Quijada Sandra, Gallegos Doris, González Claudia

Center for Micro Data, Economics Department, University of Chile, Santiago, Chile.
Center of Epidemiology and Health Policies Department, Faculty of Medicine, Universidad del Desarrollo, Concepción, Chile.
Center of Epidemiology and Health Policies of the Universidad del Desarrollo, Concepción, Chile.
Centers for Diseases Control and Prevention, Atlanta, USA.
Epidemiology and Health Policies Department, Universidad del Desarrollo, Concepción, Chile.
Panamerican Health Organization, Washington DC, USA.
Public Health Department and Pediatrics Division, Faculty of Medicine, Pontifical Catholic University of Chile, Santiago, Chile.
Section of Respiratory and Exanthematous viruses, Sub-Department of Clinical Virology, Institute of Public Health, Ministry of Health, Santiago, Chile.

DOI: 10.4236/wjcd.2013.37075                

Abstract

Objective: To know the natural history of the first wave of pandemic influenza A(H1N1)pdm09 in the Southern hemisphere, through the detection of antibodies against influenza A(H1N1)pdm09 in a selected community, to estimate the population attack rate and its variations, the consultation rates, hospitallization and mortality rates. Methodology: A representative random sample of the population of a commune in Chile (San Felipe) was interviewed and taken blood samples between January and March 2010. A study against the antibodies of the influenza A(H1N1) pdm09 virus was conducted, by the technique of the Hemaglutination Inhibition (HAI) according to standardized methodology. Subjects with antibody titers ≥1:40 were considered positive. Results: 13.5% of the population of San Felipe had antibodies against influenza A(H1N1)pdm09; this percentage reached 30% of the population between 0 and 18 years and 6.1% among those over 19 years. The age variable was the only factor that evidenced significant differences in the prevalence of antibodies. There were no significant differences related to gender, vaccination history against seasonal inluenza, or comorbidity. 51% of people with positive serology showed IN-FLUENZA-LIKE SYMPTOMS. Conclusions: A relevant percentage of subclinical disease was detected in the first pandemic

wave in Chile and the proportion of people with SARI and deaths was small. Data from epidemiological surveillance were useful to estimate the trend of TSI but not its magnitude.

Keywords

Influenza A(H1N1)pdm09; Influenza Seroprevalence

Conflicts of Interest

The authors declare no conflicts of interest.

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