Abstract
BackgroundAfrican populations are considered to be particularly vulnerable to fever illnesses, including malaria, and acute respiratory disease, owing to limited resources and overcrowding. However, the overall burden of influenza in this context is poorly defined and incidence data for African countries are scarce. We therefore studied the fever syndrome incidence and more specifically influenza incidence in a cohort of inhabitants of Dielmo and Ndiop in Sokone district, Senegal.MethodsDaily febrile-illness data were prospectively obtained from January 2012 to December 2013 from the cohort of the villages of Dielmo and Ndiop, initially dedicated to the study of malaria. Nasopharyngeal swabs were collected from, and malaria diagnosis tests (thick blood smears) carried out on, every febrile individual during clinical visits; reverse transcriptase-polymerase chain reaction was used to identify influenza viruses in the samples. Binomial negative regression analysis was used to study the relationship between the monthly incidence rate and various covariates.ResultsIn Dielmo and Ndiop, the incidence of malaria has decreased, but fever syndromes remain frequent. Among the 1036 inhabitants included in the cohort, a total of 1,129 episodes of fever were reported. Influenza was present all year round with peaks in October-December 2012 and August 2013. The fever, ILI and influenza incidence density rates differed significantly between age groups. At both sites, the adjusted incidence relative risks for fever syndromes and ILI were significantly higher in the [6–24 months) than other age groups: 7.3 (95%CI: [5.7–9.3]) and 16.1 (95%CI: [11.1–23.3]) respectively. The adjusted incidence relative risk for influenza was significantly higher for the [0–6 months) than other age groups: 9.9 (95%CI: [2.9–33.6]). At both sites, incidence density rates were lowest among adults > = 50 years.ConclusionsIn this rural setting in Senegal, influenza was most frequent among the youngest children. Preventive strategies targeting this population should be implemented.
Highlights
African countries are burdened with a very heavy load of communicable diseases in addition to other severe health problems [1]
In 2005, as a consequence of World Health Organization (WHO) advocacy, international resources were mobilized to help African countries respond to the threat of avian influenza
If only ILI had been used as the criterion for sampling, 35% of the influenza A infections 20% of the Influenza B infections would not have been detected (Table 4). This is the first study addressing fever syndromes, influenza-like illnesses and influenza infections reported over a substantial period of time by a small cohort established to study malaria
Summary
African countries are burdened with a very heavy load of communicable diseases in addition to other severe health problems [1]. Numerous studies show that influenza is prevalent in African regions [2,3]. In 2005, as a consequence of World Health Organization (WHO) advocacy, international resources were mobilized to help African countries respond to the threat of avian influenza. This involved the implementation and enhancement of influenza surveillance tools including the collection and analysis of virological and epidemiological data [3,4,5,6,7,8,9,10,11]. African populations are considered to be vulnerable to fever illnesses, including malaria, and acute respiratory disease, owing to limited resources and overcrowding. We studied the fever syndrome incidence and influenza incidence in a cohort of inhabitants of Dielmo and Ndiop in Sokone district, Senegal
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