Seroprevalence of dengue infection: a cross-sectional survey in mainland Tanzania and on Pemba Island, Zanzibar.

Objective: Evidence available to date indicates that dengue viruses 1, 2, and 3 could be among the causes of acute fever in eastern Africa. Recently, four reports on dengue infection in travelers and residents have raised concerns over the occurrence of dengue fever in mainland Tanzania and in Zanzibar. The objective of this study was to provide seroprevalence data on dengue infection in Tanzania.

Methods: This study was conducted in 2007 at two peripheral hospitals, one on Pemba Island, Zanzibar and one in Tosamaganga, Iringa Region, mainland Tanzania. Two hundred and two consecutive febrile outpatients were studied for antibodies and viral RNA to assess the circulation of dengue virus in Tanzania.

Results: A seroprevalence of 7.7% was found on Pemba Island and of 1.8% was found in Tosamaganga. No acute cases and no previous infections among patients under 11 years of age were detected.

Conclusion: These findings provide the first baseline data on dengue seroprevalence in the country. No recent dengue virus circulation in Tanzania and in the Zanzibar archipelago up until the early 1990s is reported.