Bat-Borne Orthoreovirus Linked to Mysterious Respiratory and Brain Illness in Bangladesh
Infections disease specialists have traced a mysterious illness affecting five patients in Bangladesh to Pteropine orthoreoviruses (PRVs)—a newly emerging group of bat-borne pathogens. One of the patients later died after suffering from unexplained complications, raising fresh concerns over hidden viral threats.
This marks the first recorded instance of a bat-origin orthoreovirus, a double-stranded RNA virus, being linked to acute respiratory disease and encephalitis in humans in Bangladesh. The research has been published in the journal Emerging Infectious Diseases.
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Raw Date-Palm Sap Identified as a Common Exposure
Investigators found that all five patients had recently consumed raw date-palm sap, a seasonal delicacy that bats frequently feed on during winter. The sap has already been identified as a transmission route for Nipah virus in the country.
Bats are recognized as natural hosts for a wide range of zoonotic viruses, including rabies, Nipah, Hendra, Marburg and SARS-1.
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Scientists Warn of Broader Zoonotic Spillover Risks
"Our research shows that the danger of zoonotic spillover linked to the consumption of raw date-palm sap goes well beyond Nipah virus," said Dr Nischay Mishra, Associate Professor of Epidemiology at the Center for Infection and Immunity, Columbia University Mailman School of Public Health, and the study's senior author.
He stressed the urgent need for broad-spectrum surveillance systems to detect and reduce public health threats posed by newly emerging bat-borne viruses.
Patients Initially Suspected of Nipah Virus Infection
The five patients, who hospitalized between 2022 and 2023, were initially suspected of having Nipah virus infection. However, laboratory tests repeatedly returned negative results, despite the patients displaying similar symptoms such as:
- Fever
- Vomiting
- Headaches
- Fatigue
- Excessive salivation
- Serious respiratory complications
- Neurological complications
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Advanced Viral Sequencing Reveals the Culprit
In the latest study, scientists carried out high-throughput, agnostic viral sequencing using the CII's VirCapSeq-VERT platform. Biological samples were analyzed from the five confirmed cases, alongside samples from more than 130 patients who had shown Nipah-like symptoms between 2006 and 2022.
The work formed part of a long-running Nipah virus surveillance programme led by:
- Bangladesh's Institute of Epidemiology, Disease Control and Research (IEDCR)
- The International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR,B)
- The US Centres for Disease Control and Prevention (CDC)
How VirCapSeq-VERT Detects Emerging Viruses
Dr Nishchay Mishra and his team employed VirCapSeq-VERT, a technology developed at the Centre for Infection and Immunity, to rapidly detect all known vertebrate-origin viral infections.
The system matches the sensitivity of gold-standard PCR testing, while allowing thousands of viruses to be screened simultaneously and delivering near-complete viral genome sequences.
Live Infectious Virus Confirmed in the Laboratory
Researchers also confirmed the presence of live, infectious virus through laboratory culture. All five patients suffered severe illness, although PRV infections reported in neighbouring countries have typically been milder, raising concerns that less serious cases in Bangladesh may be going undetected.
"This represents a new zoonotic spillover risk, causing respiratory and neurological complications following the consumption of raw date-palm sap, alongside the well-known threat of Nipah virus," said Dr Tahmina Shirin, Director of the Institute of Epidemiology, Disease Control and Research (IEDCR) and the National Influenza Centre (NIC) in Bangladesh.
Bats Near Patient Homes Identified as Likely Source
In more recent work, Mishra and his colleagues traced the source of infection by identifying genetically similar Pteropine orthoreoviruses in bats captured near the homes of the five patients in the Padma River Basin.
These findings, though yet to be published, strengthen the suspected animal-to-human link.
"This research offers vital evidence connecting bat reservoirs to human infection," said Ariful Islam, a bat-borne disease ecologist and epidemiologist at Charles Sturt University in Australia and co-first author of the study.
"We are now investigating how spillover occurs from bats to humans and domestic animals, and examining the wider ecology of emerging bat-borne viruses in communities along the Padma River Basin."
Technology Already Proven in Other Major Outbreak Investigations
In earlier work, Mishra and his colleagues used the same technology to:
- Uncover a previously unrecognized viral threat in transplant patients
- Identify neurological complications in an infant and COVID-19
- Trace an enterovirus infection responsible for a rare neurological disorder
- Determine the origins of chikungunya in Brazil
Beyond its use in research settings, VirCapSeq-VERT has now secured regulatory approval for clinical application.
Study Authorship
The study was co-first authored by Sharmin Sultana, Assistant Professor of Virology and Senior Scientific Officer at Bangladesh's Institute of Epidemiology, Disease Control and Research (IEDCR).
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