Overall seroprevalences reported in the different countries, and characteristics of the different studies.

We identified 47 studies with seroprevalence data. Four studies, set in Tanzania, India and Iran, were excluded from the table because they reported IgM antibodies only. Of the remaining 43 studies, seroprevalence data were available for 50 different regions and times (Table 2). Most of these (45/50) reported proportions of CHIKV IgG-positive samples and 5/50 presented seroprevalence as the overall proportion of IgG and IgM antibodies. The reports were heterogeneous in population and sampling strategies: 20/50 were based on household data, 9/50 studies were based on blood donors, 4/50 were based on pregnant women, and 3/50 were based on children only. Of all 50 reports, 23 were clinic-based and 29 were carried out during or recently after an outbreak. Among the identified seroprevalence studies, 14 reported the proportion of asymptomatic participants among seropositive samples. Of these studies, 12 were household-based, with some degree of stratification in the sampling design, and 7 were carried out in the Americas. The reported proportion of asymptomatic infections ranged from 13–65%, with no obvious geographic pattern detected.
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