Seroprevalence of Pteropine orthoreovirus in humans remain similar after nearly two decades (2001-2002 vs. 2017) in Tioman Island, Malaysia

Pteropine orthoreovirus (PRV) is an emerging zoonotic respiratory virus that can be transmitted from bats to humans. In Malaysia, aside from PRV2P (Pulau virus) being isolated from Pteropus hypomelanus sampled in Tioman Island, PRV3M (Melaka virus), PRV4K (Kampar virus), and PRV7S (Sikamat virus) were all isolated from samples of patients who reported having a disease spectrum from acute respiratory distress to influenza-like illness and sometimes even with enteric symptoms such as diarrhea and abdominal pain. Screening of sera collected from human volunteers on Tioman Island in 2001-2002 demonstrated that 12.8% (14/109) were positive for PRV2P and PRV3M. Taking all these together, we aim to investigate the serological prevalence of PRV (including PRV4K and PRV7S) among Tioman Island inhabitants again with the assumption that the seroprevalence rate will remain nearly similar to the above reported if human exposure to bats is still happening in the island. Using sera collected from human volunteers on the same island in 2017, we demonstrated seroprevalence of 17.8% (28/157) against PRV2P and PRV3M, respectively. Seropositivity of 11.4% among Tioman Island inhabitants against PRV4K and PRV7S, respectively, was described in this study. In addition, the seroprevalence of 89.5% (17/19), 73.6% (14/19), 63.0% (12/19), and 73.6% (14/19) against PRV2P, PRV3M, PRV4K, and PRV7S, respectively, were observed among pteropid bats in the island. We revealed that the seroprevalence of PRV among island inhabitants remains nearly similar after nearly two decades, suggesting that potential spill-over events in bat-human interface areas in the Tioman Island. We are unclear whether such spillover was directly from bats to humans, as suspected for the PRV3M human cases, or from an intermediate host(s) yet to be identified. There is a high possibility of the viruses circulating among the bats as demonstrated by high seroprevalence against PRV in the bats.