Zoonotic bat virus found in fruit bats sold for human consumption in Indonesia

Researchers in Indonesia have isolated two Pteropine orthoreoviruses (PRVs) from fruit bats sold for human consumption in West Java. The viruses were found in Rousettus amplexicaudatus, a bat species not previously recognised as a PRV host, and were genetically related to strains already associated with human respiratory infections. The findings reinforce concerns about wildlife trade as a direct interface for zoonotic spillover.

The study analysed 182 fruit bats collected in 2020–2021 from animal markets and suppliers across Java. Four species were represented, including 96 R. amplexicaudatus. Two virus isolates were recovered from bats obtained from a collector in Cianjur, West Java, where bats were being sold for human consumption.

A zoonotic virus family already linked to respiratory disease

Pteropine orthoreoviruses are segmented double-stranded RNA viruses associated primarily with fruit bats. Their zoonotic potential has been recognised since the identification of Melaka virus in 2006, when infection in a person exposed to a flying fox caused fever and respiratory symptoms. Other related PRVs, including Kampar, Sikamat and Miyazaki-Bali strains, have subsequently been identified in patients with respiratory disease.

Indonesia has already yielded several bat-associated PRVs, including Garut-69 and Paguyaman orthoreovirus. Experimental infection with the latter produced severe pneumonia in mice, adding to evidence that members of this group can infect mammalian hosts beyond bats.

A new bat host for PRV

The two new isolates, PRV/SJD-K30/ID/2021 and PRV/SJD-K50/ID/2021, were both recovered from R. amplexicaudatus. That is significant because this widespread fruit bat had not previously been reported as an orthoreovirus host, despite its frequent presence near human settlements and its involvement in hunting, trade and consumption. The species is also ecologically important as a pollinator and seed disperser, illustrating the need for targeted surveillance rather than indiscriminate bat control.

Genomics points to zoonotic lineages

Researchers recovered nine of the virus’s ten genomic segments.

Across most segments, the two isolates were more than 99–100% identical, but identity in the S2 segment fell to about 88.9%, suggesting possible reassortment between locally circulating PRVs. The authors caution that sequence ambiguity limits the strength of that conclusion.

Phylogenetic analyses consistently placed the viruses within the PRV group and showed close relationships with Melaka, Pulau, Cangyuan and Garut-69 viruses. Several genomic segments were most closely related to Garut-69, an Indonesian bat-associated strain linked in the study to zoonotic relevance.

Because orthoreoviruses possess segmented genomes, reassortment can generate new combinations of viral genes, potentially affecting host range or pathogenicity.

One genomic segment remains missing

The researchers were unable to recover the S1 segment, which encodes the σC attachment protein involved in cell tropism and viral dissemination.

The authors attribute this primarily to the high variability of S1, low RNA abundance or technical limitations of sequencing. Its absence means that the study cannot fully characterise determinants potentially involved in host specificity. They recommend targeted amplification of this segment in future surveillance.

Wildlife trade creates a high-risk interface

The study does not demonstrate that people became infected from these particular bats. Nor does detection of PRV imply that every exposed person is at substantial risk. What it does show is that infectious PRVs closely related to known zoonotic viruses are circulating in bats entering the human food chain.

The authors therefore call for continuous genomic surveillance at markets and other points where bats, traders, consumers and wildlife interact.

Surveillance of wildlife viruses should not focus only on the best-known pandemic threats. Lesser-known bat viruses such as PRVs may already possess the capacity for human infection, and markets where wildlife is handled and consumed provide exactly the interfaces where their emergence is most likely to become visible.