Researchers have identified a virus that jumped from animals to humans in China.
A total of 35 human infections were recorded over two and a half years.
No one has died of Langya virus infection to date, and the virus does not seem to spread between humans.
Scientists in China have identified a virus that has infected humans for the first time, but the disease is unlikely to spread from person to person, based on the current evidence.
The first person to fall ill with the newfound Langya henipavirus, or LayV, was a woman in Shandong province in late 2018, according to a peer-reviewed correspondence published in the New England Journal of Medicine.
The patient was a farmer with a history of animal exposure, so health officials suspected a possibility of disease spillover from an animal host. Testing later revealed that the virus was previously unseen in humans and may have originated in shrews.
The woman's symptoms included fever, headache, muscle aches, fatigue, cough, and nausea, according to the report. Thirty-four more people - primarily farmers in Shandong and the neighboring Henan province - reported similar symptoms and tested positive for LayV between December 2018 and May 2021.
Based on the information available, Langya virus poses a very low risk to the general population, infectious disease doctor Monica Gandhi told Insider. No one has died of Langya virus infection to date, and researchers have not found any evidence of human-to-human transmission.
"People should not be frightened about this spreading," said Gandhi, a professor of medicine at the University of California at San Francisco who was not associated with the NEJM report. "I think everyone is hyper-alert to new viruses, but I don't think this one is going to be a major threat."
The virus was detected in wild shrews
Researchers tested 25 small wild animal species for the Langya virus and found it was "predominantly detected" in shrews, according to the report. The authors concluded that the small, mole-like mammals may be a natural host for the virus.
However, the connection between humans and shrews remains to be investigated, Gandhi said. It is not yet clear if something changed to push humans closer to shrews, or vice versa, or if another animal may be involved in the chain of transmission.
Humans appear to be a dead end for the virus, but researchers said their sample was too small to be certain. They examined close contacts of nine patients infected with LayV and found no evidence of human-to-human transmission, and the people who got sick reported no common sources of exposure.
Related viruses have caused small outbreaks with some fatalities
The Langya virus is related to - but genetically distinct from - the Nipah and Hendra viruses, which have both caused fatal infections in humans. However, people who got sick with Langya virus had milder symptoms in comparison, Gandhi noted.
All of the 26 patients found to be infected with LayV alone reported fevers. About half of them experienced fatigue, decreased white blood cell count, and cough. A few people experienced more severe symptoms, such as impaired kidney and liver function.
People infected with previous henipaviruses in the past experienced similar fevers and flu-like symptoms, often with signs of respiratory illness. Fatality rates for Nipah and Hendra viruses range between 40 and 70%, according to the US Centers for Disease Control and Prevention.
Still, Nipah and Hendra viruses have caused relatively small outbreaks compared to COVID-19 - only seven human cases of Hendra virus have been reported since 1994, and Nipah virus infected some 300 people across Malaysia and Singapore in 1999.
'We're in a different age now'
Another key difference is that scientists today are better prepared to identify new viruses and make vaccines if necessary, Gandhi said.
"We're in a different age now, where I hope that we never have to go through what we went through with SARS-CoV-2, and where we can control things better," she said.