Scientists Discover Previously Undetected Bat-Borne Virus Infecting Humans in South Asia

Researchers investigating Nipah-like illnesses in Bangladesh have uncovered evidence of another bat-borne virus circulating in humans.

Researchers studying infectious diseases have found evidence of Pteropine orthoreovirus (PRV), a bat-associated orthoreovirus, in stored throat swabs and virus cultures from five people in Bangladesh. These patients were originally believed to have Nipah virus infection but later tested negative.

The finding expands the list of animal-to-human viruses known to infect people in Bangladesh and indicates that PRV may be an overlooked cause of illnesses that resemble Nipah. The results were published in the journal Emerging Infectious Diseases.

Each of the five patients had recently consumed raw date-palm sap—a sweet liquid that bats also drink, particularly during the winter season—and a well-established route of Nipah virus transmission in Bangladesh. Bats are known to harbor a wide range of viruses capable of infecting humans, including rabies, Nipah, Hendra, Marburg, and SARS-CoV-1.

“Our findings show that the risk of disease associated with raw date palm sap consumption extends beyond Nipah virus,” said Nischay Mishra, PhD, associate professor of epidemiology at the Center for Infection and Immunity (CII), Columbia University Mailman School of Public Health, and senior author of the study. “It also underscores the importance of broad-spectrum surveillance programs to identify and mitigate public health risks from emerging bat-borne viruses.”

Detecting an Overlooked Virus

From December 2022 through March 2023, five patients were hospitalized with symptoms typically linked to Nipah virus infection (including fever, vomiting, headache, fatigue, increased salivation, and neurological). Laboratory testing using PCR and serology ruled out Nipah virus in all cases.

To investigate further, the research team applied high-throughput, agnostic viral capture sequencing (VCS) to patient samples. This approach revealed genetic material from PRV in archived throat swabs, and live virus was successfully grown from three of the samples, confirming active infection.

The patients were identified through a Nipah virus surveillance program run collaboratively by the Institute of Epidemiology, Disease Control and Research (IEDCR), Bangladesh; the International Centre for Diarrheal Disease Research, Bangladesh (icddr,b); and the U.S. Centers for Disease Control and Prevention (CDC).

Viral Capture Sequencing (VCS) is a patented technology developed in the CII at Columbia University to rapidly screen for all viral infections of vertebrates, including infections of bats. It is as sensitive as the gold-standard polymerase chain reaction (PCR) assays while enabling simultaneous testing for thousands of viruses and providing near-complete genome sequences. A correlate method, Bacterial Capture Sequencing (BCS), allows detection of pathogenic bacteria and genes for antimicrobial resistance. Both VCS and BCS are approved for clinical and research use.

All five patients experienced severe disease, although PRV infections reported elsewhere in neighboring countries have often been milder, suggesting that less severe cases in Bangladesh may be undetected.

“A new addition of zoonotic spillover causes respiratory and neurological complications following consumption of raw date palm sap next to Nipah virus infection,” says Tahmina Shirin, PhD, Director, Institute of Epidemiology, Disease Control, and Research (IEDCR), as well as the National Influenza Centre (NIC) in Bangladesh.

Tracing the Source of Infection

In a study conducted more recently that was supported by the U.S. Department of Agriculture, Mishra and colleagues identified the source of infections by identifying genetically similar Pteropine orthoreoviruses in bats captured in proximity to the five human cases near the Padma River Basin (unpublished data).

“This [research] provides critical evidence linking bat reservoirs to human infection. We are now working to understand the spillover mechanisms from bats to humans and domestic animals, as well as the broader ecology of emerging bat-borne viruses in communities along the Padma River Basin,” says Ariful Islam, bat-borne disease ecologist and epidemiologist at Charles Sturt University, Australia, and co-first author of the study.

Reference: “Bat Reovirus as Cause of Acute Respiratory Disease and Encephalitis in Humans, Bangladesh, 2022–2023” by Sharmin Sultana, Ariful Islam, James Ng, Sunil Kumar Dubey, Manjur Hossain Khan, Cheng Guo, Mohammed Ziaur Rahman, Joel M. Montgomery, Syed Moinuddin Satter, Tahmina Shirin, W. Ian Lipkin, Lisa Hensley and Nischay Mishra, December 2025, Emerging Infectious Diseases.
DOI: 10.3201/eid3112.250797

The study’s co-first author is Sharmin Sultana, assistant professor of Virology and Senior Scientific Officer at the Institute of Epidemiology, Disease Control and Research (IEDCR) in Bangladesh. Additional authors include James Ng, Sunil Kumar Dubey, Cheng Guo, and W. Ian Lipkin of the CII; Manjur Hossain Khan at IEDCR in Bangladesh; Mohammed Ziaur Rahman and Moinuddin Satter at icddr,b in Bangladesh; Joel M. Montgomery at the CDC’s National Center for Emerging and Zoonotic Infectious Diseases; and Lisa Hensley at the Zoonotic and Emerging Disease Research Unit, in the United States Department of Agriculture.

The research was supported with funds provided by United States Department of Agriculture agreements with Columbia University (NACA-58-3022-2-021, NACA- 58-3022-4-053).

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