Abstract
BackgroundThere is limited information about the epidemiology of influenza in Africa. We describe the epidemiology and seasonality of influenza in Morocco from 1996 to 2009 with particular emphasis on the 2007–2008 and 2008–2009 influenza seasons. Successes and challenges of the enhanced surveillance system introduced in 2007 are also discussed.MethodsVirologic sentinel surveillance for influenza virus was initiated in Morocco in 1996 using a network of private practitioners that collected oro-pharyngeal and naso-pharyngeal swabs from outpatients presenting with influenza-like-illness (ILI). The surveillance network expanded over the years to include inpatients presenting with severe acute respiratory illness (SARI) at hospitals and syndromic surveillance for ILI and acute respiratory infection (ARI). Respiratory samples and structured questionnaires were collected from eligible patients, and samples were tested by immunofluorescence assays and by viral isolation for influenza viruses.ResultsWe obtained a total of 6465 respiratory specimens during 1996 to 2009, of which, 3102 were collected during 2007–2009. Of those, 2249 (72%) were from patients with ILI, and 853 (27%) were from patients with SARI. Among the 3,102 patients, 98 (3%) had laboratory-confirmed influenza, of whom, 85 (87%) had ILI and 13 (13%) had SARI. Among ILI patients, the highest proportion of laboratory-confirmed influenza occurred in children less than 5 years of age (3/169; 2% during 2007–2008 and 23/271; 9% during 2008–2009) and patients 25–59 years of age (8/440; 2% during 2007–2009 and 21/483; 4% during 2008–2009). All SARI patients with influenza were less than 14 years of age. During all surveillance years, influenza virus circulation was seasonal with peak circulation during the winter months of October through April.ConclusionInfluenza results in both mild and severe respiratory infections in Morocco, and accounted for a large proportion of all hospitalizations for severe respiratory illness among children 5 years of age and younger.
Highlights
Since 1948, the World Health Organization (WHO) Global Influenza Surveillance Network has provided a platform to monitor circulating influenza types and subtypes to make informed decisions about the composition of influenza vaccine [1]
Using influenza surveillance data from Morocco from 1996–2009, we describe the seasonality of influenza virus circulation, identify age groups accounting for a large proportion of influenza-associated outpatient visits and hospitalizations, and discuss the successes and challenges of expanding influenza surveillance during 2007–2009
Among the severe acute respiratory illness (SARI) cases, children less than 5 years of age accounted for 86% of cases during 2007– 2008 and 79% of cases during 2008–2009
Summary
Since 1948, the World Health Organization (WHO) Global Influenza Surveillance Network has provided a platform to monitor circulating influenza types and subtypes to make informed decisions about the composition of influenza vaccine [1]. Influenza sentinel surveillance, which includes the collection of epidemiological and virological data, provides a tool to monitor the circulating types and subtypes of influenza to assess the burden of influenza in the community and to rapidly detect the appearance of novel influenza subtypes in the human population. These data can be used to understand geographic, temporal, and biologic differences in circulating influenza strains and to monitor for the emergence and evolution of pandemic strains [3,4,5]. Successes and challenges of the enhanced surveillance system introduced in 2007 are discussed
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