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Langya henipavirus: New virus found in China could be ‘tip of the iceberg’ for undiscovered pathogens, researchers say

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Hong-Kong
CNN

More surveillance is needed on a new virus discovered in dozens of people in eastern China that may not cause the next pandemic, but suggests how easily viruses can travel undetected from animals to humans, scientists say.

The virus, called Langya henipavirus, infected nearly three dozen farmers and other residents, according to a team of scientists who believe it may have spread directly or indirectly. for people of shrews – small mole-like mammals that live in a wide variety of habitats.

The pathogen caused no reported deaths, but was detected in 35 unrelated fever patients at hospitals in Shandong and Henan provinces between 2018 and 2021, the scientists said — a finding consistent with scientists’ long-standing warnings that animal viruses regularly go undetected. in people all over the world.

“We greatly underestimate the number of these zoonotic cases in the world, and this (Langya virus) is just the tip of the iceberg,” said emerging virus expert Leo Poon, a professor at the University of Hong Kong’s School of Public Health. , who was not involved in the latest investigation.

The first scientific study on the virus, published last week as a correspondence from a team of Chinese and international researchers in the New England Journal of Medicine, received worldwide attention amid heightened concerns about disease outbreaks. Hundreds of thousands of new cases of Covid-19 are still reported worldwide every day, nearly three years since the novel coronavirus behind the pandemic was first discovered in China.

However, the researchers say there is no evidence that the Langya virus spreads between humans or that it caused a local outbreak of connected cases. More research on a larger subset of patients is needed to rule out human-to-human spread, she added.

Experienced emerging infectious disease scientist Linfa Wang, who was part of the research team, told CNN that while the new virus was unlikely to evolve into another “disease X” event, such as a previously unknown pathogen causing an epidemic or pandemic. “It does show that such zoonotic spillover events are more common than we think or know.”

To reduce the risk of an emerging virus becoming a health crisis, “it is imperative to conduct active surveillance in a transparent and internationally collaborative manner,” said Wang, a professor at Duke-National University of Singapore Medical School.

The first indications of the presence of a new virus emerged when a 53-year-old farmer sought treatment at a hospital in Qingdao city in Shandong province in December 2018 with symptoms including fever, headache, cough and nausea, according to documentation from the researchers.

Since the patient reported having had contact with animals in the past month, she took part in an additional screening conducted at three hospitals in eastern China aimed at identifying zoonotic diseases.

When examining this patient’s test samples, scientists discovered something unexpected – a virus never seen before, related to the Hendra and Nipah viruses, highly lethal pathogens from a family not typically known for spreading easily to humans. on human.

Over the next 32 months, researchers at the three hospitals screened for this virus in similar patients, eventually finding it in 35 people, who had a range of symptoms in addition to fever, including cough, fatigue, headache and nausea.

Nine of those patients were also infected with a known virus, such as the flu, so the source of their symptoms was unclear, but researchers believe the symptoms in the remaining 26 may have been caused by the new henipa virus.

Some showed severe symptoms such as pneumonia or abnormalities of thrombocytopenia, a platelet disorder, according to Wang, but their symptoms were far from those seen in Hendra or Nipah patients, and none of the group died or were admitted to the ICU. Although they all recovered, they were not monitored for longer-term problems, he added.

Of that group of 26, all but four were farmers, and while some were reported by the same hospital as the first case discovered, many others were found in Xinyang, more than 700 kilometers (435 miles) away in Henan.

Since similar viruses were known to circulate in animals from southwestern China to South Korea, it was “not surprising” to see spillovers to humans over such long distances, Wang explained.

There was “no close contact or common exposure history among the patients” or other signs of human-to-human spread, Wang and his colleagues wrote in their findings. This suggests cases were sporadic, but more research was needed, they said.

Once they knew that a new virus was infecting people, the researchers, including scientists from Beijing and disease control officials from Qingdao, set to work to see if they could find out what was infecting the patients. They tested domestic animals where patients lived for traces of previous infection with the virus, and found a small number of goats and dogs that may have previously had the virus.

But the real breakthrough came when they tested samples taken from small wild animals caught in traps — and found 71 infections in two species of shrews, leading the scientists to suggest these small, rodent-like mammals could be where the virus naturally circulates. .

What remains unclear is how the virus got to humans, Wang said.

Further investigations into the Langya henipa virus would follow and should be conducted not only in the two provinces where the virus was found, but more widely in China and beyond, he said.

China’s National Health Commission has not immediately responded to a request for comment on whether it continues to monitor for new infections of the virus.

Globally, 70% of emerging infectious diseases are thought to have passed through contact with animals, in a phenomenon scientists say has accelerated as growing human populations expand into wildlife habitats.

China has seen major outbreaks of emerging viruses in the past two decades, including SARS in 2002-2003 and Covid-19 – both discovered for the first time in the country and of viruses believed to come from bats.

The devastating effects of both diseases – particularly Covid-19 that has killed more than 6.4 million people worldwide to date – demonstrate the importance of quickly identifying cases of new viruses and sharing information about potential risks.

Scientists not involved in the new research agreed that more work was needed to understand the Langya virus and confirm the latest findings, saying the discovery underscored the importance of tracking which viruses spread from animals to animals. people to spread.

“Since this (new henipavirus) may not just be circulating in China, it is important to share this information and allow others to prepare or do further research in their own country,” Poon said in Hong Kong.

Scientists say critical questions need to be answered about how widespread the new virus may be in nature, how it gets into humans and how dangerous it is to human health — including the possibility of it spreading between humans or gaining this ability if it continues to jump from animals to humans.

The geographic scope of where the infections were found “suggests that this risk of infection is quite widespread,” said virologist Malik Peiris, also of the University of Hong Kong, adding studies important elsewhere in China and neighboring countries “in order to extend the geographic reach.” detect this virus in animals (shrews) and in humans.”

He also said the latest findings pointed to the high number of undetected infections passing from wildlife to humans, and to the need for systematic studies to understand not just this virus, but the broader picture of human infection with animal viruses. in the wild.

“This is important so that we are not surprised by the next pandemic when – not if – it comes,” he said.

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