- More than 30 people in China have been sickened by a newly identified virus.
- The symptoms of Langya henipavirus, or LayV, include fever, fatigue, cough, muscle aches, pain, nausea, headache, and vomiting.
- Researchers believe the virus was spread from animals to humans, in this case from shrews.
- So far, none of the people infected have died.
- Experts have also not found evidence that the virus can be transmitted between people.
An international team of scientists identified a new virus, called LayV, which they say was potentially transmitted to humans from shrews — another example of a zoonotic disease, like the coronavirus that causes COVID-19 and many other pathogens that spread from animals to people.
However, none of the people infected with the new virus died. In addition, scientists say there is no evidence of viral spread among people, although they admit their sample size was too small to be certain.
The researchers — based in China, Singapore, and Australia — detailed their discovery on August 4 in The New England Journal of Medicine.
Where was the virus discovered?
Researchers identified LayV during routine monitoring of patients for potential zoonotic diseases in three hospitals in eastern China between 2018 and 2021.
The first patient was a 53-year-old woman who visited a hospital in December 2018 with fever, headache and other symptoms. Researchers sequenced the virus’ genome from a throat swab sample taken from the woman.
During the study period, researchers identified 35 other people infected with LayV. Of these, 26 were infected with only LayV (no other viruses). All people in the study had a recent history of animal exposure.
What symptoms does the virus cause?
Fever was the most common symptom among people infected with LayV, occurring in all patients. Other symptoms included fatigue, cough, muscle aches, pain, nausea, headache, and vomiting.
Some people also had a low blood platelet count, low white blood cell count, impaired liver function, or impaired kidney function.
None of the patients in the study died of illness caused by LayV infection.
Although the risk from the virus appears to be low, Anthony P. Schmitt, PhD, a professor of molecular virology at The Pennsylvania State University in University Park, Pa., pointed out that fewer than 40 people were infected. So these may not be representative of the whole population.
“If the virus were to cause a larger outbreak affecting hundreds or thousands of people, some with pre-existing conditions, it is possible that we would see cases of more serious illness,” he said.
Where did the virus come from?
To determine the potential origin of LayV, researchers tested samples from domestic goats, dogs, pigs, cattle, and 25 species of wild small animals in the villages of the infected patients.
They found LayV antibodies in a small number of goats and dogs (5% or fewer of the tested animals). Among the wild animals, they found LayV genetic material (RNA) “predominantly” in shrews (27% of the tested animals).
“[This finding] suggests that the shrew may be a natural reservoir of LayV,” the researchers said. However, it’s not clear whether people were infected directly from the shrews or through an intermediate animal.
Dr. Benhur Lee, a professor of microbiology at the Icahn School of Medicine at Mount Sinai in New York City, wrote on Twitter that the “evidence is strong that LayV [has] sporadically spilled over into humans from shrews, causing pneumonia and flu-like symptoms.”
In addition, although “no deaths were reported and there is no evidence for onwards human transmission … continued surveillance is important,” he said.
Does the virus spread between people?
Of the 35 people infected by LayV since 2018, none of the cases seem to be linked, researchers said in the paper.
They also did contact tracing of nine patients with 15 close contacts, with no evidence that infected people spread the virus onto their close contacts.
However, researchers said the number of infected patients and close contacts were “too small” to determine if LayV could spread between people.
Schmitt said because the 35 infections in this study occurred over several years and there is no evidence of person-to-person transmission, “there does not appear to be any immediate cause for alarm.”
Long-term, though, it’s another story.
The study findings suggest that people are coming into contact with animals infected with LayV and occasionally becoming infected themselves.
“Each time that happens, the virus presumably has a chance — perhaps only a small chance, but a chance nonetheless — to adapt within its new human host and become better able to transmit to other people,” said Schmitt.
“The concern is that with enough chances, eventually we will get unlucky and a virus will adapt in just the right way to cause a serious outbreak,” he added.
The spillover of viruses from animals to people — who, we often forget, are also animals — is not new. It’s been going on for as long as people have been around.
However, there is concern that climate change, unregulated wildlife trade, deforestation, and urbanization increase the risk of zoonotic transmission.
Schmitt said it’s difficult to know if these kinds of spillover events are increasing or if we are just getting better at detecting them.
“In the past, when someone got sick as a result [of one of these transmissions], it would remain a ‘mystery illness,’” he said. “Now, sometimes we solve the mystery, and these spillovers that used to be hidden are revealed.”
Are there closely related viruses that infect people?
LayV belongs to a family of viruses known as Paramyxoviridae, which also includes the measles, mumps, and respiratory syncytial virus (RSV) viruses.
More closely related to LayV are two other henipaviruses known to infect people — Hendra virus and Nipah virus. These cause a severe influenza-like illness which is often fatal, according to the U.S. Centers for Disease Control and Prevention.
Fruit bats are the natural host for both of these viruses, but they can also infect other animals. People can get Hendra virus from contact with infected horses or the tissues or body fluids of infected horses.
Nipah virus can be transmitted to people through infected bats or pigs or exposure to bat urine. Person-to-person transmission has been reported with Nipah virus, but not Hendra virus.
However, researchers said LayV is most closely related to Mojiang henipavirus, a rat-borne virus that was first identified in southern China in 2012 after three miners developed severe pneumonia and died.
Lee and his colleagues studied how Mojiang henipavirus enters cells and found that it uses a method that is distinct from Hendra virus and Nipah virus.