Dengue outbreaks: a constant risk for Reunion Island. Results from a seroprevalence study among blood donors.

BACKGROUND: Immunity against dengue virus (DENV) on Reunion Island could play an important role in the risk of dengue outbreaks but is rather unknown. A study was performed to estimate seroprevalence of antibodies against DENV among blood donors. METHODS: An age- and sex-stratified sample of 1825 sera was randomly selected. RESULTS: Overall seroprevalence was 3.1% (95% CI: 2.2-3.9%); seroprevalence increased with age and was much higher in women than in men. CONCLUSION: The low level of herd immunity is consistent with the absence of an endemic circulation of DENV, and makes it probable that Reunion Island will face future outbreaks.