Bangladeshi researchers have uncovered an emerging bat-borne virus in archived throat swabs and viral cultures from five patients initially thought to be infected with Nipah virus (NiV).

The discovery of Pteropine orthoreovirus (PRV), which raises the concern that dangerous bat viruses may be silently co-circulating with NiV, prompted the authors to recommend the consideration of PRV in the diagnosis of patients with NiV-like illness.

The patients were admitted to hospitals in Bangladesh for acute respiratory illness and encephalitis from December 2022 to March 2023. Polymerase chain reaction (PCR) and blood tests were negative for NiV, but high-throughput genetic sequencing detected PRV, and the researchers were able to grow virus in culture from the samples of three patients.

All patients had recently eaten raw date-palm sap, which is also a food source for fruit bats and the main route of NiV spillover from bats to humans.

“Bats are the natural reservoir of numerous known and novel zoonotic viruses, including rabies, Nipah, Hendra, Marburg, and severe acute respiratory syndrome viruses,” the researchers wrote. “PRV is classified under the genus Orthoreovirus, family Reoviridae, which includes Nelson Bay virus (NBV), identified in Australia in 1968. Zoonotic potential of NBV was confirmed in 2006, when a human case occurred in Melaka, Malaysia.”

The researchers’ findings were published in Emerging Infectious Diseases.

The patients were identified through an NiV surveillance program operated by the Institute of Epidemiology, Disease Control and Research and the International Centre for Diarrheal Disease Research in Bangladesh and the US Centers for Disease Control and Prevention (CDC).