Environmental surveillance of arboviruses in wastewater: A pilot study in the Philippines

Arboviruses, including Japanese encephalitis virus (JEV), dengue virus (DENV), chikungunya virus (CHIKV), and Zika virus (ZIKV), circulate in the Philippines. However, the feasibility of wastewater-based surveillance (WBS) for these viruses has not been evaluated in the country. This pilot study applied WBS to monitor arboviruses in the Philippines. Influent samples collected from wastewater treatment plants (WWTPs; n = 27) and open drainages (ODs; n = 24) from March 2024 to August 2024 were subjected to centrifugation, RNA extraction, and reverse transcription-quantitative polymerase chain reaction. JEV demonstrated the highest detection frequency in wastewater samples (41/51; 80%), with comparable concentrations across wastewater systems, indicating a possible wide range of environmental inputs from both human and animal hosts. DENV (8/51; 16%) and CHIKV (5/51; 10%) showed lower detection frequencies, whereas ZIKV was undetected in all samples. JEV and DENV were both detected in WWTPs and ODs, whereas CHIKV was detected only in one WWTP. JEV concentrations in sixteen quantifiable samples from all wastewater systems ranged between 3.19 and 4.75 log₁₀ copies/L, while CHIKV concentration in one quantifiable sample from WWTP A was 4.17 log₁₀ copies/L. Regardless of season, JEV, DENV, and CHIKV were detected in wastewater samples, suggesting possible ongoing low-level circulation and environmental contamination during both hot dry and rainy seasons. These findings addressed a crucial regional gap in arboviral WBS research and revealed that WBS can be applied to arboviruses using existing laboratory capacities in resource-limited settings.