Scientists have identified a previously overlooked bat-borne virus infecting humans in Bangladesh, raising concerns that dangerous zoonotic diseases may be circulating undetected in the population.

Researchers found that several patients initially suspected of having the deadly Nipah virus were instead infected with a different pathogen known as Pteropine orthoreovirus (PRV). While PRV shares similarities with Nipah in terms of symptoms and transmission routes, it is genetically distinct.

The discovery was made by a research team led by scientists from Columbia University’s Mailman School of Public Health, who analyzed stored throat swab samples and virus cultures from five patients. All individuals had tested negative for Nipah virus despite showing classic Nipah-like symptoms.

Genetic testing confirmed the presence of live virus in multiple samples, providing clear evidence of active human infection. The findings suggest that bat-related viruses may be infecting people more frequently than previously recognized.

Investigators found a common link among all patients: recent consumption of raw date palm sap. The sweet sap, widely consumed during winter in Bangladesh, is often contaminated by bats and is already known as a major transmission route for Nipah virus.

“This shows that the health risks linked to consuming raw date palm sap go beyond Nipah virus alone,” said Nischay Mishra, senior author of the study and a researcher at Columbia University’s Center for Infection and Immunity. He added that PRV should now be considered when doctors assess patients with Nipah-like illness.

Bats are natural hosts to many dangerous viruses, including Nipah, Hendra, Marburg, rabies, and SARS-CoV-1, making human exposure a significant public health concern.

Between December 2022 and March 2023, the infected patients were hospitalized with symptoms such as fever, vomiting, headache, fatigue, excessive salivation, and neurological complications.

The cases were detected through a Nipah virus surveillance program jointly run by Bangladesh’s Institute of Epidemiology, Disease Control and Research (IEDCR), the International Centre for Diarrheal Disease Research, Bangladesh (icddr,b), and the US Centers for Disease Control and Prevention (CDC).

The research was published in the journal Emerging Infectious Diseases. Scientists involved in the study warned that many similar infections may be going undiagnosed, underscoring the need for broader surveillance and improved diagnostic testing for emerging bat-borne viruses.