New Nipah-like bat virus in Bangladesh is becoming more deadly, scientists warn

A mystery illness in Bangladesh, initially thought to be a Nipah infection outbreak, is actually due to another emerging and potentially deadly bat-borne virus, scientists warned in a new study.

Between December 2022 and March 2023, five patients were admitted to hospitals in Bangladesh, with symptoms including fever, vomiting, headache, fatigue, increased salivation, and neurological issues.

All five patients had also consumed raw date-palm sap, a sweet liquid also enjoyed by bats, which are a known vector for Nipah infections in the country. However, all of them tested negative for Nipah.

The patients were discharged within weeks, but three complained of persistent fatigue, disorientation, and breathing and walking difficulties, and one of them died in 2024 after deteriorating health and unexplained neurologic ailments.

Now, scientists have found that the patients actually had Pteropine orthoreovirus (PRV), another bat-borne pathogen.

Until now, bats have been known to be the natural reservoir of numerous deadly zoonotic viruses, such as rabies, Nipah, Hendra, Marburg, and SARS.

PRV infections reported elsewhere in neighbouring countries have often been milder, but not so in these newly documented cases.

“All 5 patients had severe respiratory and neurologic symptoms, but PRV infections in Malaysia, Indonesia, and Vietnam were associated with milder respiratory disease,” scientists wrote in the study published in the journal Emerging Infectious Diseases.

Researchers suspect the virus may have undergone a reassortment of its genetic sequence, resulting in changes to its transmissibility and virulence.

The latest findings add PRV to the list of zoonotic viruses detected in humans in Bangladesh and suggest that it should be considered in the differential diagnosis of Nipah-like illnesses.

“Our findings show that the risk of disease associated with raw date palm sap consumption extends beyond Nipah virus,” said Nischay Mishra, an 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,” Dr Mishra said.

Researchers also identified genetically similar PRVs in bats captured in proximity to the five human cases near the Padma river basin.

“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,” said Ariful Islam, another author of the study.

In areas where raw date palm sap is consumed, researchers call for medical surveillance and diagnoses of respiratory illnesses to include tests for PRV, NiV, and other bat-borne viruses.