An international team of scientists identified a new virus that likely jumped to humans from shrews, a mammal that resembles a mouse, in a possible case of zoonotic spillover.
In a letter published in the New England Journal of Medicine last week, researchers from China, Singapore, and Australia reported the discovery of the Langya henipavirus. Infection has been found in 35 people—mostly farmers—in the eastern Chinese provinces of Shandong and Henan from 2018 to 2021, with symptoms such as fever, fatigue, cough, and anorexia.
Of the 35 patients, 26 were infected only with the Langya virus and not any other pathogen. More than half developed blood-cell abnormalities, nine suffered impaired liver function, and two had kidney damage. All eventually recovered.
“So far these cases have not been fatal or very serious. It is therefore safe to say that this new virus should be greeted with alarm, not panic,” Wang Linfa, a leading zoonotic disease expert from the Duke-NUS Medical School in Singapore and one of the researchers, said in an interview with Chinese media.
The team conducted contact tracing with 15 family members of 9 patients and did not find any human-to-human transmission, but it could not determine whether that is possible due to the small sample size.
“More detailed investigation of close contacts of these cases needs to be carried out, including antibody testing for the new virus, to confirm the lack of human-to-human transmission,” Malik Peiris, a virologist from the University of Hong Kong, who was not involved in the study, told VICE World News.
The discovery of the Langya virus has sparked concerns in part because it belongs to the same family as the Hendra virus and Nipah virus, which originated from fruit bats and could cause lethal neurologic and respiratory diseases in humans. The Nipah virus, for instance, can spread directly from human to human and has a case mortality rate of 40 to 75 percent.
But comparing the Langya virus with the two other henipaviruses may not be fair, Simon Reid, an epidemiologist at the University of Queensland, told VICE World News.
“The phylogenetic trees they have are quite different and branch off quite early, so they are distantly related,” Reid said, referring to diagrams that show a species’ evolutionary development. “That’s potentially a good thing. It means that they might be quite different viruses, in terms of the disease they cause.”
The researchers took samples from domestic and wild animals at the villages where the patients lived. While some goats and dogs also tested positive for the virus, it was found in 71 of 262 shrews captured with snap traps. The high percentage suggests the terrestrial animal may be a natural reservoir of the virus, they said.
But some experts believe bats are the more likely source of the virus.
Shrews aren’t an obvious host due to their short life expectancy of around a year, Peter John Hudson, a biology professor at the Pennsylvania State University, told NBC News.
Bats, in comparison, could live for decades and naturally harbor henipaviruses, as well as coronaviruses and filoviruses. “It’s possible that the natural reservoir hosts are bats and these other small mammals are potentially just infected from the same source,” Reid said.
Scientists estimated that up to 75 percent of new or emerging infectious diseases are zoonotic in origin, meaning they came from animals. China is vulnerable to zoonotic spillover due to its large population and agricultural workforce, as well as its highly biodiverse ecology. A wildlife market in the Chinese city of Wuhan was suspected to be the source of COVID-19 in such a zoonotic spillover event.
Reid also attributed the more frequent discovery of new viruses in China to their unique acute respiratory infection surveillance system. “They’re doing something here that no one else does. They’re more likely to find these viruses because they’re looking for them,” he said.
A recent study that mapped the risk of spillover in Southeast Asia suggested about 66,000 people are infected each year with SARS-related coronaviruses from bats, but the majority of cases went undetected by surveillance programs and clinical studies, and did not cause an outbreak.
The risk of zoonotic spillover would only grow as human disruption of the natural environment increases.
“We need to be careful, because there are many more viruses like this in nature, and if a different virus jumps into humans, it might be a different story,” said Wang, the zoonotic disease expert at Duke-NUS Medical School in Singapore.