China — Between 2018 and August 2022, Chinese researchers identified 35 people infected with a new animal virus in eastern China. These cases were reported in The New England Journal of Medicine (NEJM) on August 4. When asked by Nature about this emerging virus that has until now flown under the radar, scientists said that they were not overly concerned because the virus doesn’t seem to spread easily between people nor is it fatal.
Researchers think that the virus is carried by shrews. It might have infected people directly or through an intermediate animal.
First Identified in Langya
In the NEJM publication, the authors describe 35 cases of infection with a virus called Langya henipavirus (LayV), since 2018. It is closely related to two other henipaviruses known to infect people — Hendra virus and Nipah virus (see box). The virus was named Langya after the town in Shandong province in China where the first patient identified with the disease was from, explained co-author Linfa Wang, PhD, a virologist at Duke-NUS Medical School in Singapore.
Langya can cause respiratory symptoms such as fever, cough, and fatigue. Hendra virus and Nipah virus also cause respiratory infections and can be fatal (see box), the article in Nature reports.
Hendra and Nipah
According to the World Health Organization (WHO), Nipah virus, which was discovered in 1999, is a new virus responsible for a zoonosis that causes the disease in animals and humans who have had contact with infected animals. Its name comes from the location where it was first identified in Malaysia. Patients may have asymptomatic infection or symptoms such as acute respiratory infection and severe encephalitis. The case fatality rate is between 40% and 75%.
Nipah virus is closely related to another recently discovered (1994) zoonotic virus called Hendra virus, which is named after the Australian city in which it first appeared. On that day in July 2016, 53 cases were identified involving 70 horses. These incidents remained confined to the northeastern coast of Australia.
Nipah virus and Hendra virus belong to the Paramyxoviridae family. “While the members of this group of viruses are only responsible for a few limited outbreaks, the ability of these viruses to infect a wide range of hosts and cause a disease leading to high fatalities in humans has made them a public health concern,” stated the WHO.
Related to Measles
The research team identified LayV while monitoring patients at three hospitals in the eastern Chinese provinces of Shandong and Henan between April 2018 and August 2021. Throughout the study period, the researchers found 35 people infected with LayV, mostly farmers, with symptoms ranging from a cough to severe pneumonia. Participants were recruited into the study if they had a fever. The team sequenced the LayV genome from a throat swab taken from the first patient identified with the disease, a 53-year-old woman.
The LayV genome showed that the virus is most closely related to Mojiang henipavirus, which was first isolated in rats in an abandoned mine in the southern Chinese province of Yunnan in 2012. Henipaviruses belong to the Paramyxoviridae family of viruses, which includes measles, mumps, and many respiratory viruses that infect humans. Several other henipaviruses have been discovered in bats, rats, and shrews from Australia to South Korea and China, but only Hendra, Nipah, and now LayV are known to infect people, according to Nature.
Animal Origin Likely
Because most patients stated in a questionnaire that they had been exposed to an animal during the month preceding the onset of their symptoms, the researchers tested goats, dogs, pigs, and cattle living in the villages of infected patients for antibodies against LayV. They found LayV antibodies in a handful of goats and dogs and identified LayV viral RNA in 27% of the 262 sampled shrews. These findings suggest that the shrew may be a natural reservoir of LayV, passing it between themselves “and somehow infecting people here and there by chance,” Emily Gurley, PhD, MPH, an infectious diseases epidemiologist at Johns Hopkins University in Baltimore, Maryland, told Nature.
The researchers did not find strong evidence of LayV spreading between the people included in the study. There were no clusters of cases in the same family, within a short time span, or in close geographical proximity. “Of the 35 cases, not a single one is linked,” said Wang, which Gurley considered good news. It should be noted, however ,”that the study did retrospective contact tracing on only 15 family members of nine infected individuals, which makes it difficult to determine how exactly the individuals were exposed,” reported Nature.
Vigilance Is Needed
Should we be worried about a potential new epidemic? The replies from two experts interviewed by Nature were reassuring. “There is no particular need to worry about this virus, but ongoing surveillance is critical,” said Edward Holmes, an evolutionary virologist at the University of Sydney in Australia. Regularly testing people and animals for emerging viruses is important to understand the risk for zoonotic diseases — those that can be transmitted from other animals to humans, he said.
It is still not clear how people were infected in the first place — whether directly from shrews or an intermediate animal, said Gurley. That’s why a lot of research still needs to be done to work out how the virus is spreading in shrews and how people are getting infected, she added.
Nevertheless, Gurley finds that large outbreaks of infectious diseases typically take off after a lot of false starts. “If we are actively looking for those sparks, then we are in a much better position to stop or to find something early.” Still, she noted that she didn’t see anything in the data to “cause alarm from a pandemic-threat perspective.”
Though there is not currently any cause for worry of a new pandemic, vigilance is crucial. Holmes says there is an urgent need for a global surveillance system to detect virus spillovers and rapidly communicate those results to avoid more pandemics, such as the one sparked by COVID-19. “These sorts of zoonotic spillover events happen all the time,” he said. “The world needs to wake up.”
This article was translated from the Medscape French edition.
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