Abstract
Background: Before its recent spread, serological studies conducted between the 1960s and the 1990s showed the wide presence of Zika virus in Africa, but in recent years, limited data are available on its circulation in the African population. The aim of this study was to evaluate the immunity to Zika virus in a selected cohort of healthy subjects from West Africa between 2007 and 2012. Methods: Human serum samples were collected in 2007 and in 2011/2012 from a cohort of 2-29-year-old subjects from Mali, Senegal, and The Gambia. A sample that tested positive by Zika virus IgG ELISA and by Zika virus microneutralization test was defined as positive. Findings: In 2007, the highest seroprevalence to Zika was 21·9% (95%CI 14·08-31·47), found in Senegal among 18-29-year-old subjects. In 2011/2012, the highest seroprevalence, 22·7% (95%CI 13·79-33·79), was found still in Senegal, but in 11-17-year-old subjects. During the two study periods the lowest prevalence was found in Mali, where few positive cases were found and only in 18-29-year-old subjects. The Gambia showed an intermediate seroprevalence. In the three countries, seroprevalence to Zika virus was strongly associated with increasing age. Interpretation: This study contributes to understanding Zika virus circulation within three different ecological and demographic contexts with scarce or no data currently available. Results showed that Zika virus circulated actively in West Africa between 2007 and 2011/2012, but with some geographic specificity. As seropositivity to Zika virus increases with age, women are at high risk to be infected during their reproductive age. Funding Statement: None. Declaration of Interests: The authors declare no conflict of interests. Ethics Approval Statement: The present study was approved by Ethic Committees in Mali, Senegal and The Gambia.
Highlights
Zika virus (ZIKV) is a Flavivirus transmitted to humans mainly by Aedes mosquitoes that was first isolated in Uganda in 1947 [1,2]
ZIKV gained new attention after its spread in the Pacific and to the Americas [5], and in recent years serological studies were conducted in Africa, documenting the presence of ZIKV antibodies in humans [6,7,8,9]
In 2011/2012, the highest prevalence of all ZIKV positive samples continued to be in Senegal (13.7%, 95%confidence interval (CI) 9.4–19.14), followed by The Gambia
Summary
Zika virus (ZIKV) is a Flavivirus transmitted to humans mainly by Aedes mosquitoes that was first isolated in Uganda in 1947 [1,2]. Serological data suggest that ZIKV transmission has occurred among humans, animals and mosquitoes throughout tropical Africa for more than 70 years; ZIKV epidemics were never reported, and fewer than 20 human infections were recorded [3] between its isolation and the first large epidemic, occurring in Micronesia in 2007 [4]. ZIKV gained new attention after its spread in the Pacific and to the Americas [5], and in recent years serological studies were conducted in Africa, documenting the presence of ZIKV antibodies in humans [6,7,8,9]. Transmission of ZIKV has been reported in Guinea-Bissau (African lineage) and Angola (Asian lineage) [13,14]
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