Abstract
BackgroundOver the last decade, capacity for influenza surveillance and research in West Africa has strengthened. Data from these surveillance systems showed influenza A(H1N1)pdm09 circulated in West Africa later than in other regions of the continent.MethodsWe contacted 11 West African countries to collect information about their influenza surveillance systems (number of sites, type of surveillance, sampling strategy, populations sampled, case definitions used, number of specimens collected and number of specimens positive for influenza viruses) for the time period January 2010 through December 2012.ResultsOf the 11 countries contacted, 8 responded: Burkina Faso, Cote d’Ivoire, Mali, Mauritania, Niger, Nigeria, Sierra Leone and Togo. Countries used standard World Health Organization (WHO) case definitions for influenza-like illness (ILI) and severe acute respiratory illness (SARI) or slight variations thereof. There were 70 surveillance sites: 26 SARI and 44 ILI. Seven countries conducted SARI surveillance and collected 3114 specimens of which 209 (7%) were positive for influenza viruses. Among influenza-positive SARI patients, 132 (63%) were influenza A [68 influenza A(H1N1)pdm09, 64 influenza A(H3N2)] and 77 (37%) were influenza B. All eight countries conducted ILI surveillance and collected 20,375 specimens, of which 2278 (11%) were positive for influenza viruses. Among influenza-positive ILI patients, 1431 (63%) were influenza A [820 influenza A(H1N1)pdm09, 611 influenza A(H3N2)] and 847 (37%) were influenza B. A majority of SARI and ILI case-patients who tested positive for influenza (72% SARI and 59% ILI) were children aged 0–4 years, as were a majority of those enrolled in surveillance. The seasonality of influenza and the predominant influenza type or subtype varied by country and year.ConclusionsInfluenza A(H1N1)pdm09 continued to circulate in West Africa along with influenza A(H3N2) and influenza B during 2010–2012. Although ILI surveillance systems produced a robust number of samples during the study period, more could be done to strengthen surveillance among hospitalized SARI case-patients. Surveillance systems captured young children but lacked data on adults and the elderly. More data on risk groups for severe influenza in West Africa are needed to help shape influenza prevention and clinical management policies and guidelines.
Highlights
Over the last decade, capacity for influenza surveillance and research in West Africa has strengthened
A recent review estimates that each year over 250,000 African children aged less than 5 years are hospitalized with influenza and have influenza-associated hospitalization rates more than 3 times higher than those of children in industrialized countries [2]
Since 2006, 30 countries have implemented or improved influenza surveillance systems and 14 countries in Africa have received National Influenza Center (NIC) recognition from the World Health Organization (WHO) [4,5,6,7]. Ten of these countries regularly report to the WHO’s Global Influenza Surveillance and Response System (GISRS). These countries have provided essential information on risk factors for severe influenza-associated illness including Human immunodeficiency virus (HIV) and tuberculosis infection, which are relatively common in sub-Saharan Africa [8,9,10,11]
Summary
Capacity for influenza surveillance and research in West Africa has strengthened. Since 2006, 30 countries have implemented or improved influenza surveillance systems and 14 countries in Africa have received National Influenza Center (NIC) recognition from the World Health Organization (WHO) [4,5,6,7] Ten of these countries regularly report to the WHO’s Global Influenza Surveillance and Response System (GISRS). These countries have provided essential information on risk factors for severe influenza-associated illness including HIV and tuberculosis infection, which are relatively common in sub-Saharan Africa [8,9,10,11]
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