Long-term circulation of Zika virus in Thailand: an observational study

Little is known about the historical and current risk of Zika virus infection in southeast Asia, where the mosquito vector is widespread and other arboviruses circulate endemically. Centralised Zika virus surveillance began in Thailand in January, 2016. We assessed the long-term circulation of Zika virus in Thailand.

In this observational study, we analysed data from individuals with suspected Zika virus infection who presented at hospitals throughout the country and had biological samples (serum, plasma, or urine) tested for confirmation with PCR at the National Institute of Health laboratories in Bangkok. We analysed the spatial and age distribution of cases, and constructed time-resolved phylogenetic trees using genomes from Thailand and elsewhere to estimate when Zika virus was first introduced.