Seroprevalence of Dengue, Zika, and Chikungunya Viruses in Humans and Colocated Macaques in Thailand and Cambodia.

BACKGROUND

Arboviruses-short for "arthropod-borne viruses"-are transmitted to humans and animals by infected arthropods. Aedes mosquito-borne arboviruses such as dengue virus (DENV), Zika virus (ZIKV), and chikungunya virus (CHIKV) impose major public health burdens in Southeast Asia. The potential role of sylvatic reservoirs, such as macaques, in maintaining arboviral transmission remains unclear.

METHODS

We assessed the role of sylvatic reservoirs in arboviral circulation by examining serological evidence of exposure to DENV, ZIKV, and CHIKV among humans and macaques living in close proximity in endemic regions. Cross-sectional serosurveys were carried out during 2019-2022, involving 649 humans and 398 macaques colocated across 4 sites in Thailand (Hua Hin, Laem Chabang, and Muang Lop Buri) and Cambodia (Chbar Mon). Seropositivity was evaluated using plaque reduction neutralization tests (PRNT50).

RESULTS

We found overall higher seropositivity rates across arboviruses among human populations compared to macaques (38.5%-74.4% vs 0%-8.0%, respectively, using PRNT50 cutoff). Virus seroprevalence differed between Thai and Cambodian cohorts and age was the only significant predictor of human seropositivity in multivariate analyses.

CONCLUSIONS

The low seropositivity among macaques suggests a limited role of macaques in sustaining and amplifying urban arboviral cycles; rather, low-level macaque seropositivity may signal virus spillback from human populations.