Dengue virus seroprevalence among febrile patients in Bamako, Mali: Results of a 2006 surveillance study

Background: Dengue viruses (DENV) are endemic in over 100 countries worldwide, and annually 50 to 100 million people are infected by one of the four DENV serotypes, whereas over 2.5 billion people are at risk for infection. West African countries lack the surveillance to determine the true incidence of dengue; hence, this disease is likely significantly underestimated. In Mali, ∼14 million people are potentially at risk of acquiring a dengue infection. Methods and Findings: A serosurvey for DENV was conducted on 95 human serum samples obtained from the Institute National de Recherche en Sante Publique in 2006. DENV-specific IgM and IgG enzyme-linked immunosorbent assays were performed on all samples, and a subset was tested using the plaque-reduction neutralization test against the DENV and yellow fever virus (YFV). Samples collected during the acute infection (0-5 days postonset of symptoms) were tested for dengue NS1 antigen and reverse-transcriptase polymerase chain reaction for Flaviviruses, Alphaviruses, and Bunyaviruses RNA. A total of 87 (93%) of samples were positive for anti-DENV IgG antibodies. Of a subset of 13 IgG positive samples, 2 samples neutralized monotypically against DENV-1 and -2, whereas 3 others neutralized broadly against YFV and multiple DENV. Although no polymerase chain reaction positives were found, DENV NS1 was detected in 1 of the 20 acute samples tested. Conclusions: Of the 93 human serum samples tested, the dengue prevalence based on dengue IgG enzyme-linked immunosorbent assay results was 93%. Three DENV specific positive samples and two YFV positives were identified by plaque-reduction neutralization test. Finally, one sample tested positive for dengue NS1, thus suggestive of an acute infection within 14 days of obtaining the sample from the patient. Based on these serological data from this study, YFV and DENV appear to be co-circulating in Mali.