Scientists in China have raised urgent concerns over new viruses that were discovered in bats with the potential to spill over into humans, causing high fatalities. After testing bats, experts found 22 viruses—20 of which have never been seen before.

According to experts, two of the viruses were of particular concern, as they were closely related to the deadly Nipah and Hendra viruses, both of which are emerging zoonotic pathogens belonging to the genus Henipavirus within the family Paramyxoviridae. They lead to brain swelling and severe respiratory and neurological disease in humans and animals, with high mortality rates. They are considered high-consequence pathogens due to their potential for outbreaks and lack of specific treatments.

Nipah spreads mainly through fruit bats but can also spread through pigs and other animals. It can cause severe symptoms, including fever and headache, and has already been flagged as a priority pathogen by the World Health Organisation because of its potential to trigger a global pandemic. Experts say it has the ability to kill up to 70 per cent of its victims, with outbreaks frequently reported in Bangladesh, India, Malaysia, the Philippines, and Singapore.

Hendra virus, on the other hand, is rare and leads to severe and often fatal disease in both infected horses and humans. The natural host of the virus has been identified as being fruit bats of the Pteropodidae family, Pteropus genus. HeV was identified during the first recorded outbreak of the disease in the Brisbane suburb of Hendra, Australia.

Scientists at the Yunnan Institute of Endemic Disease Control and Prevention detected two worrying viruses – described as the "evolutionary cousins" of Nipah and Hendra – while testing the kidneys of bats in the Yunnan province of China.

The bats lived in orchards close to villages, sparking concerns that fruit eaten by inhabitants and livestock may get contaminated and risk wider transmission. "Bats have been implicated in a number of major emerging disease outbreaks, including Hendra, Nipah, Marburg and Ebola virus disease, severe and acute respiratory syndrome (SARS), Middle East respiratory syndrome or MERS and Covid-19," researchers wrote in the journal PLOS Pathogens.

"Bat-borne viruses are transmitted to humans either through direct contact with bats or via the ingestion of food or water contaminated with bat saliva, faeces, or urine," they added.

The study, led by Dr Yun Feng, pointed out that previous research looking at the disease-spreading potential of bats has only focused on their faeces. However, scientists said the bats' kidneys also presented potential transmission risks, as the viruses that live there may be excreted through urine.

"The kidney can harbour important zoonotic pathogens, including the highly pathogenic Hendra and Nipah viruses," scientists said.

They looked inside the kidneys of 142 bats from ten species, which were collected over four years in five areas of Yunnan province. Using advanced genetic sequencing, the team found at least 22 viruses – out of which 20 were never seen before.