Sentinel surveillance for influenza and other respiratory viruses in Côte d'Ivoire, 2003-2010

Abstract

Background: Many countries in Africa have lacked sentinel surveillance systems for influenza and are under-represented in data used for global vaccine strain selection.

Objectives: We describe 8 years of sentinel surveillance data and the contribution of influenza and other viruses to medically attended influenza-like illness (ILI) in Côte d'Ivoire.

Methods: Sentinel surveillance was established in 2003. Nasopharyngeal (NP) specimens and epidemiologic data are collected from persons of all ages presenting with ILI at sentinel sites. Respiratory specimens have been tested for influenza using various viral and molecular diagnostic methods. A subset of 470 specimens collected from children aged 0-5 years were tested for multiple respiratory viruses using RT-PCR.

Results: From 2003 to 2010, 5074 NP specimens were collected from patients with ILI. Overall, 969/5074 (19%) of these specimens tested positive for influenza. Seasonal influenza A(H1N1) viruses predominated during 5 years and influenza A(H3N2) viruses predominated during 3 years. Influenza B viruses cocirculated with influenza A viruses during each year from 2004 to 2010. Seasonal peaks in influenza circulation were observed during the months of May, June, and October, with the largest peak corresponding with the primary rainfall season. Of 470 specimens collected from children under aged 5 who were tested for multiple respiratory viruses, a viral respiratory pathogen was detected in 401/470 (85%) of specimens. Commonly detected viruses were RSV (113 of 470 specimens, 24%), rhinoviruses (85/470, 18%), influenza (77/470, 16%), and parainfluenza (75/470, 16%).

Conclusion: In Côte d'Ivoire, there is a significant annual contribution of influenza and other respiratory viruses to medically attended ILI.

Figure 1

Location of influenza sentinel sites in Côte d’Ivoire.

Figure 2

Distribution of influenza types and subtypes by month, Côte d’Ivoire 2007–2010.

Figure 3

Monthly percentage of sentinel ILI cases testing positive for influenza viruses, by average rainfall (mm), temperature (C) and relative humidity (%), Côte d’Ivoire, 2007–2010.