Fever, altered mental status, abnormal gait, breathing difficulties, encephalitis… All these symptoms are common in people infected with the virus Nipah (NiV), which caused a brief panic in February 2026 following some new cases in IndiaBut this virus is not the only one to cause such symptoms: a study by the Institute of Epidemiology, Disease Control and Research in Bangladesh and Columbia University in the United States has just revealed that some Bangladeshi patients suspected of being infected with the Nipah virus were actually infected with another virus. Their discovery, published in December 2025 in the journal Emerging Infectious Diseases, shows that the diagnosis of this disease is much more complicated than expected, and highlights the increased danger of zoonosis in the region.
A virus that is transmitted through the sap of the date palm
The virus in question is the Pteropine orthoreovirus (PRV), of the reovirus family (Reoviridae), which had already been identified in patients in Malaysia in 2023. It is an RNA virus, meaning its genetic material is stored in the form of RNA (like the flu or Covid-19 viruses). It is common in bats, particularly those that feed on date palm sap, and can thus contaminate it with their excrementHowever, humans also consume this sap in Bangladesh, particularly during the winter.
Long-term consequences
This is likely how the patients were infected with the virus. These five Bangladeshis were hospitalized between December 2022 and March 2023 in different parts of Bangladesh, suspected of having Nipah virus infection because they all presented with the characteristic symptoms. However, their tests for the virus were negative. But they all had in common that they had consumed date palm sap during the 14 days before the onset of symptoms.
Fortunately for the patients, they were all discharged from the hospital two to three weeks after their admission. However, only two of them fully recovered: one died in August 2024 from neurological complications, and the other two still experienced symptoms, such as fatigue and difficulty walking and breathing, more than 15 months after hospitalization. The authors note, however, that they only studied cases of severe illness, and therefore it is entirely possible that this virus could also cause milder or even asymptomatic infections.
A virus that travels easily
The viruses found in these patients were genetically similar to others identified in several bat species in Indonesia, Zambia, Uganda, China, and even Australia, highlighting how easily viruses can travel via these flying mammals. The genetic material of these viruses also showed that they had undergone extensive mixing, even with other virus species. This underscores the speed at which these viruses can evolve through this mixing, which could make them even more dangerous. The authors therefore emphasize the need to test all patients presenting with these symptoms for a multitude of bat-borne viruses, not just Nipah virus. This measure is particularly important in regions where date palm sap is consumed.
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