Chikungunya virus (CHIKV) is responsible for a rapidly increasing but poorly understood infection burden globally. Bangladesh experienced its first reported outbreak in 2008. Despite a number of subsequent isolated outbreaks, culminating in an enormous nationwide epidemic in 2017, very little is known about the burden or dynamics of chikungunya within the country, and the risk factors for infection. We conducted a nationally representative seroprevalence survey in 2016 in 70 randomly selected communities across the country. Individuals provided blood samples, which were tested for the presence of IgG antibodies to CHIKV. We also trapped and speciated mosquitoes. We found that 69/2,938 (2.4%) of individuals were seropositive to CHIKV. Seropositive individuals were concentrated in the centre and south of the country. We found that being seropositive to dengue virus (aOR 3.11 [95% CIs: 1.17, 24.45]) and male sex (aOR 0.29 [95% CIs: 0.01, 0.96]), were significantly associated with CHIKV seropositivity, however, Aedes presence, income, and travel history were not. Using a spatial prediction model, we estimate that at the time of the study, 4.99 million people in the country had been infected with CHIKV. These findings highlight high population susceptibility prior to the major outbreak in 2017 and that historic outbreaks must have been spatially isolated.

The authors have declared no competing interest.

This study was funded by from ERC 804744 and the CDC. The authors declare no conflicts of interest.

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The icddr,b and CDC ethical review boards approved of this study (protocol number PR-14058). All participating adults gave written informed consent. Children involved in the study had written, informed consent provided on their behalf by parents/guardians.

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