In December 2018, a 53-year-old woman presented to a hospital in China with flu-like symptoms. She was infected with a henipavirus, a class that includes some dangerous pathogens like the Nipah virus, which has a mortality rate of 40% to 75%.

But the virus infecting the patient was genetically distinct from other henipaviruses scientists had seen before. It came from a new pathogen now known as the Langya virus.

Scientists have detected 34 more Langya cases in two eastern Chinese provinces through 2021, according to findings released last week by a research team in China, Singapore and Australia. None of the patients died.

For this reason, scientists are not yet alarmed. There are also no signs of human-to-human transmission; the patients who were studied did not appear to be spreading the virus to close contacts, nor did they have a history of common exposures. Langya therefore appears to cause infrequent and sporadic infections, and is most likely transmitted from animals to humans.

Most patients had close contact with animals before becoming ill, according to Zhu Feng and Tan Chee Wah, researchers at Duke-National University of Singapore Medical School who co-authored the paper.

Yet other henipaviruses that spread from animals to humans can have serious consequences. The Hendra virus, which can lead to respiratory disease or inflammation of the brain, has a 57% mortality rate. The Nipah virus produces similar symptoms.

“This is a family of viruses that we know are of concern, and it appears that this group has now added a new strain of viruses capable of severe disease,” said Vaughn Cooper, professor of evolutionary biology at the University of Pittsburgh. did not participate in the research. Increased surveillance is likely to pick up more cases of Langya, he said.

The virus appears different from Hendra and Nipah viruses, said Peter John Hudson, a Penn State biology professor who studies pathogens.

“It’s closely associated with henipaviruses, but it might not even belong to that family,” he said.

Shrews or fruit bats could be the host animal

Feng and Chee Wah said the patients’ symptoms were “relatively mild”, although four developed pneumonia.

All reported cases had fever. About half suffered from fatigue, coughing and muscle aches. About a third developed nausea, headache, vomiting and impaired liver function. Two patients had impaired renal function.

The research team suggested that shrews – small mouse-like mammals that feed on insects – could be natural hosts for the Langya virus. After examining 25 species of small wild animals, the team found that 27% of shrews carried the Langya virus, the highest share for any species in the research.

“There are clearly repeated transmission events from what appears to be a common reservoir in shrews,” Cooper said. “The team did a very good job of evaluating the alternatives and finding this as the most likely explanation.”

Reservoir hosts are species in which a virus circulates, often harmlessly, which can transmit it to humans or other animals. But shrews aren’t an obvious animal host due to their short lifespans, Hudson said.

“At this point, we don’t know who the reservoir host is,” he said. “I expected it to be a flying fox.”

Flying foxes are fruit bats and Hendra and Nipah viruses are known to originate from. In the case of Hendra virus, the virus is usually transmitted from bats to horses; it then infects humans through animal excretions or bodily fluids.

People can catch the Nipah virus from bats or pigs through direct contact with animals, their bodily fluids, or contaminated food. There have also been some “little stutter chains” of human-to-human transmission from Nipah, Hudson said.

Hudson speculated that flying foxes could transmit the virus to rodents or shrews, which could then transmit it to humans. Cooper guessed that people could also be exposed through contact with the feces of infected animals, but scientists have yet to determine this to be true.

Feng and Chee Wah also said they “could not rule out the possibility that dogs and goats could be an intermediate host”, since they detected the virus in 2% of goats and 5% of dogs studied.

Scientists may find more henipaviruses in the future

Cooper said it is an achievement that the researchers detected the Langya virus without a reported death.

“Normally it takes serious results to motivate a group to find a new virus, and although they are hospitalized patients, there are no deaths, so it is a merit that they hunted,” he said.

Hudson attributed the discovery, in part, to strong disease tracking efforts.

“Since the first SARS outbreak, we have seen a sharp increase in surveillance in China for a number of these viruses. With the development of new virus identification techniques, there has certainly been a global increase in the surveillance, and it has accelerated in the past five years,” Hudson said.

But even so, the two experts said, many unstudied and undocumented henipaviruses are likely to circulate in animals.

Ideally, scientists would identify new pathogens before they spread to humans, Hudson said: “If you want to prevent the next pandemic, you actually have to stop these processes that go from reservoir hosts to humans.”