Low Prevalence of Zika Virus RNA Among Thai Blood Donors

BACKGROUND: mosquitoes, which thrive in tropical regions. However, reports indicate that asymptomatic carriers can inadvertently transmit ZIKV through blood and blood components. METHODS: To evaluate the risk of ZIKV transmission via blood donation, we investigated the prevalence of ZIKV RNA among healthy Thai blood donors over two consecutive rainy seasons. From January 2020 to September 2021, a total of 64,705 blood donations from 56,145 individual donors were screened for ZIKV RNA at Thailand's National and Regional Blood Centers. Testing was performed using the cobas Zika test, with initially reactive samples subjected to further confirmation via in-house real-time RT-PCR. Donors with confirmed positive results were recalled for follow-up testing. The complete coding genome was sequenced and analyzed phylogenetically to determine the ZIKV strain lineage. RESULTS: ZIKV RNA was detected in four confirmed-reactive blood donations, equating to a prevalence of 0.006% (95% CI: 0.0000, 0.0002) or approximately 1 in 16,176 donations. These cases originated from four individual donors who were asymptomatic at the time of donation but subsequently developed mild symptoms, which were resolved within a week. Genetic analysis revealed that the identified ZIKV strains belonged to the Asian lineage. CONCLUSIONS: The very low prevalence of ZIKV RNA in blood donations from healthy Thai donors over the 20-month study period suggests that routine ZIKV nucleic acid screening for blood donations is not currently warranted.