Title of Contribution: A prospective cohort study of the seasonality and burden of pediatric influenza in Nicaragua

Session I – Gordon, Aubree – Abstract 1 of 2 – Young Investigator Applicant

Author(s): Aubree Gordon1, Saira Saborio2, Guillermina Kuan3, Elsa Videa4, Oscar Ortega4, Art Reingold1, Angel Balmaseda2, Eva Harris5

Affiliation(s): 1Division of Epidemiology, School of Public Health, University of California, Berkeley, California; 2National Center for Diagnosis and Reference, Ministry of Health, Managua, Nicaragua; 3Socrates Flores Vivas Health Center, Ministry of Health, Managua, Nicaragua; 4Sustainable Sciences Institute, Managua, Nicaragua; 5Division of Infectious Diseases, School of Public Health, University of California, Berkeley, California

Abstract:
Little is known about the epidemiology and burden of influenza in tropical developing countries. To study the burden and seasonality of influenza in children in Nicaragua, we are conducting a prospective multi-year pediatric cohort study, the Nicaraguan Influenza Cohort Study.  In June 2007, we began a community-based cohort study embedded within an ongoing dengue cohort study of children 2 to12 years of age living in Managua, Nicaragua, to examine the incidence of laboratory-confirmed influenza and to analyze risk factors associated with influenza virus infection. Nasal and throat swabs are collected from a random 25% of all cohort participants who present for a medical appointment with influenza-like-illness (ILI), defined as fever or a history of fever with cough and/or sore throat of 4 days or less duration.  Samples are tested for influenza viruses by RT-PCR; viral isolation is performed on all RT-PCR-positive samples.  Virus isolates are currently undergoing full-length sequencing as a part of the Influenza Genome Sequencing Project.  All samples are also tested for Respiratory Syncytial Virus (RSV), Parainfluenza (PIV) 1-3, Adenovirus, and Human Metapneumovirus (HMPV) to investigate the contribution of each virus to overall respiratory illness in the cohort.  Weekly influenza incidence in the cohort is estimated by applying the percentage of samples positive for influenza in the calendar week to the total number of children who presented with ILI, divided by the person-time for that week.   A total of 4,352 children between the ages of 2 and 12 years old were followed for every primary care appointment between June 2007 and October 2008.  To date, 1,621 swab samples have been collected and tested for influenza virus A and B, of which 388 (23.9%) were positive by RT-PCR.  The estimated incidence of influenza in the cohort during the first year of the study is 16.2 cases per 100 person-years.  A peak of influenza A/H2N3 was observed in June 2007, and a peak of influenza A/H1N1 and influenza B was documented in June, 2008. These initial results indicate that influenza is a major health concern in Nicaraguan children and suggest that Nicaragua experiences a peak of influenza activity between May and July of each year.  RSV, PIV-1, PIV-2, PIV-3, Adenovirus, and HMPV were also detected swab samples.  This is the first large-scale prospective study to provide data on the incidence and seasonality of influenza and other respiratory viral diseases in Central America.