A man in eastern China may be the first confirmed human case of infection with the H10N3 strain of bird flu, China’s National Health Commission (NHC) said Tuesday.
The 41-year-old man from Jiangsu province, located northwest of Shanghai, was hospitalized April 28 after developing fever and other symptoms.
He was diagnosed with the infection on May 28, according to Reuters, but is now stable and ready to be discharged from the hospital.
The health commission said the infection was a result of accidental cross-species transmission. The risk of widespread transmission is low, Chinese officials said, and there are no other human cases of H10N3 reported elsewhere in the world.
Avian influenza Type A viruses infect the respiratory and gastrointestinal tracts of birds and have been found in more than 100 different species of wild birds around the world, according to the U.S. Centers for Disease Control and Prevention.
While these viruses don’t normally infect humans, birds can shed virus in their saliva, mucous and feces, the CDC says. Human infections can occur if enough virus gets into a person’s eyes, nose, or mouth.
The CDC says two strains of bird flu viruses have been mostly responsible for human infection and mortality: H7N9 and H5N1. Symptoms of avian influenza A virus infections can range from mild to severe and include conjunctivitis and influenza-like illness such as fever, cough, sore throat and muscle aches.
Symptoms can also be accompanied by nausea, abdominal pain, diarrhea, vomiting and severe respiratory illness, according to the CDC.
While it’s possible for some of these viruses to jump from birds to humans, they so far don’t have the capability of transmitting between humans, said Jürgen Richt, a professor at Kansas State University and director of the Center on Emerging and Zoonotic Infectious Diseases with the National Institutes of Health.
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“This is our biggest fear,” said Richt, who also directs the Center of Excellence for Emerging and Zoonotic Animal Diseases for the Department of Homeland Security. “If they were to transmit human to human, then we would be at a worse situation than COVID-19 in terms of case fatality rates.”
This is because bird flu strains can be particularly deadly among human populations. According to the World Health Organization, the case-fatality rate of H7N9 is roughly 30%; H5N1 is 60%.
It may be unlikely the H10N3 strain can transmit between humans, Richt said, but scientists can’t know for sure until they learn its genetic code and conduct epidemiological surveillance to determine if any other contacts were infected.
“The reason for that is that avian influenza viruses spread among avian species using different receptors than mammalian influenza viruses,” he said. “In order for these viruses to transmit (among humans), the virus needs to adapt. There’s several adaptation steps and, so far, this has not happened with avian flu viruses.”