On Tuesday, China's National Health Commission (NHC) announced that a 41-year-old man in the city of Zhenjiang, in the Jiangsu province, was infected with the H10N3 strain of bird flu, Reuters reports. It is the first case of a human infection with H10N3.
The NHC said that man was hospitalized on April 28 after developing a fever and other symptoms, but he wasn't diagnosed until last Friday, May 28. Luckily, he was stable enough to be discharged from the hospital, and other infections weren't detected among his close contacts, per Reuters. The NHC said the chances of large-scale spread of the H10N3 strain were low, according to Reuters.
With public health anxiety at an all-time high due to the COVID-19 pandemic, it's understandable why news of a virus newly-detected in a human may be alarming for some. Here's what you need to know—and why experts don't believe this is a major concern.
What is H10N3?
H10N3 is a form of avian influenza—aka "bird flu"—according to the Centers for Disease Control and Prevention (CDC). These viruses normally infect wild aquatic birds, as well as domestic poultry and other bird and animal species, but they don't normally infect humans, though rare cases of infection have been reported per the CDC.
In those rare cases, saliva, mucous, or feces from infected birds get into a person's eyes, nose, or mouth. These (again, very rare) infections normally happen after unprotected contact with infected birds or surfaces contaminated with avian influenza viruses, the CDC says.
As far as the new H10N3 strain goes, because it's only been reported in one person, there isn't much information on it right now, Waleed Javaid, MD, director of infection prevention and control at Mount Sinai Downtown in New York, tells Health. "We know very little because there's only been one reported case at this time," says Dr. Javaid, though he adds that the strain appears to have been circulating among birds for a while.
Are experts concerned about large-scale spread of H10N3?
Since there were no other cases of H10N3 among the patient in Zhenjiang's close contacts, we don't know if H10N3 can be spread via human-to-human transmission, Dr. Javaid says. However, while it's still too early to say definitively that it can't, the fact that the individuals the patient had come in contact with didn't show signs of having been infected with the strain is good news. If human-to-human transmission of H10N3 was a huge threat, we'd likely see far more cases right now, says Dr. Javaid.
Given what we know right now—that only one person has been infected—we don't need to sound any alarms. "One case—probably too premature to start worrying about it," says Dr. Javaid, who adds that the CDC hasn't issued any sort of warning about the strain.
Are there any other avian influenza viruses that can infect humans?
Currently, there are few avian influenza strains known to infect humans: H5, H7, and H9—usually in the form of H5N1 and H7N9 viruses, per the CDC. And while they're rare in the general population, these infections happen most commonly among those who work with poultry, Amesh Adalja, MD, senior scholar at Johns Hopkins Center for Health Security, tells Health. "There's often one-off infections," he says.
According to the CDC, the first human cases of the H5N1 virus infection were identified in Hong Kong in 1997—and while a small number of health care workers and household contacts got infected with the virus, it didn't spread any further. Smaller clusters have been found periodically throughout Asia since, and more than 700 human infections globally have been reported to the World Health Organization (WHO) since November 2003, according to the CDC. Though these human infections are rare, about 60% of cases prove fatal, per the CDC.
The first human infections of the H7N9 strain were reported to the WHO in March of 2013, the organization reports, adding that those infected had been in contact with "animals or with an animal environment." According to an update from the WHO posted in September of 2018, among 1,567 laboratory-confirmed cases of the strain, there were 615 deaths.
Overall, per the CDC, "Asian H5N1 and Asian H7N9 viruses have not been detected in people or birds in the United States."
It's also important to remember that context is key regarding bird flu strains, Dr. Adalja says, adding that infectious disease experts are constantly monitoring for new strains that might pose a public health threat. That said, it's possible that this one case of the H10N3 strain will be the only human case of the infection—but only time will tell, says Dr. Javaid.
What are the symptoms of avian influenza, in general?
Just generally speaking, based on what experts know about bird flu overall, the symptoms often look like a typical influenza-like illness ranging from mild to severe infections, per the CDC. That means symptoms can include:
- Influenza-like illness (fever, cough, sore throat, muscle aches)
- Abdominal pain
- Severe respiratory illness (shortness of breath, difficulty breathing, pneumonia, respiratory failure)
- Neurologic changes (altered mental status, seizures)
Avian influenza viruses, however, cannot be diagnosed by signs and symptoms alone—the CDC says laboratory testing is needed, usually through swabs collected from the upper respiratory tract of an infected person.
As for treatment of avian influenza viruses, the CDC recommends what's known as a neuraminidase inhibitor—like oseltamivir, peramivir, and zanamivir—a type of antiviral drug that can block reproduction of the virus. And the best way to avoid avian influenza viruses is to avoid exposure like direct or close contact with infected poultry (though, again, that is not an issue in the US).
So what happens now?
Because the strain is "not a very common virus," as Filip Claes, regional laboratory coordinator of the Food and Agriculture Organization's Emergency Centre for Transboundary Animal Diseases at the regional office for Asia and the Pacific, told the Associated Press, experts will have to analyze the genetic data of the virus to see if it resembles old viruses or if it's a brand-new mix.
But right now, since experts aren't concerned about wide-scale spread, and because they don't know if the virus can be spread via person-to-person contact, there's nothing to be worried about at this time, says Dr. Javaid. "Knowing about this is important," he says, "[but] right now, it's more of a wait, watch, and see."
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