Why it's worth keeping 'close eye' on new Langya virus that's infecting dozens in China

When scientists published a letter in early August announcing a little-understood virus was infecting dozens of people in China, it echoed headlines from more than two-and-a-half years earlier.

A novel pathogen. People falling ill with fever, cough, fatigue. Both humans and animals getting infected.

Sound familiar? 

In this case, the letter was about the arrival of the Langya henipavirus, and its likely links to animal populations, which might call to mind the early days of COVID-19 — or, as the virus behind it was known then, the "novel coronavirus."

"There is a bit of déjà vu here," said Dr. Ari Bernstein, interim director of the Center for Climate, Health, and the Global Environment at the Harvard T.H. Chan School of Public Health. 

"This is yet another example of a pathogen moving from an animal to a person and, as we know, that is the root cause of most of the emerging infections in the world."

But when it comes to newly discovered viruses, some cause more concern than others, and not all instances of animal-to-human transmission will spark massive outbreaks or trigger years-long pandemics. Many, however, are worth keeping an eye on in the scientific world — since more hosts means more opportunities for a virus to mutate, potentially unlocking new ways to infect, transmit, and spread.

And, as several scientists who spoke to CBC News agreed, the world needs to brace for more viruses like this spilling over into human populations in the years ahead, with Langya just the latest example.

"The fact that there is a virus that has made the jump into people, and that has evidence of exposure in other species, is already sufficient information for us to say we should be keeping a close eye on it," said Simon Anthony, a researcher and associate professor in the department of pathology, microbiology and immunology at the U.C. Davis School of Veterinary Medicine.

In the case of Langya, the virus was identified through surveillance of people with fevers and recent animal exposure in eastern China. 

Scientists based in China published their findings in a letter in the New England Journal of Medicine in early August, noting that between April 2018 and August 2021, 35 patients infected with the virus were reported in China's Shandong and Henan provinces.

The vast majority of cases were farmers, who faced a range of symptoms, including fever, fatigue, cough, nausea, headaches, and vomiting.

But there are no reports of human-to-human transmission — at least not yet.

There was no close contact or common exposure history among the patients, "which suggests that the infection in the human population may be sporadic," the researchers wrote.