What Is H3N8 Bird Flu Risk for Humans in U.S?

A Chinese woman has become the first person to die from an uncommon form of bird flu in only the third recorded case of a human being infected with the virus.

The 56-year-old from the southern province of Guangdong was reported to have been infected with avian influenza A(H3N8), also known as "H3N8 bird flu."

According to a statement from the World Health Organization (WHO) released on April 11, she fell ill on February 22, 2023 before being hospitalized for severe pneumonia on March 3, 2023. She died 13 days later, on March 16, 2023.

H3N8 bird flu is a different virus to the H5N1 bird flu currently spreading between birds, other animals and humans in the U.S. and worldwide. H3N8 viruses were first identified in wild birds in the 1960s, and have since also been detected in other animals, including dogs, cats, seals and horses. H3N8 causes little to no signs of disease in either domestic poultry or wild birds, the WHO states.

H3N8 bird flu in humans has never been detected in the U.S., but different strains of the virus have been found in mammals and birds in the U.S. previously. According to a 2012 paper published in the journal mBio, an outbreak occurred amongst harbor seals in New England in 2011 that led to 162 seals dying.

The statement said it is likely that the Guangdong woman contacted H3N8 due to exposure to poultry, possibly at a live poultry market. However, the exact source is yet to be confirmed.

"The patient had multiple underlying conditions. She had a history of exposure to live poultry before the onset of the disease, and a history of wild bird presence around her home," the WHO said in the statement. "No close contacts of the case developed an infection or symptoms of illness at the time of reporting."

According to the Centers for Disease Control and Prevention (CDC), the only previous two cases of H3N8 bird flu in humans were also recorded in China, in April and May 2022, both of which were children with regular exposure to poultry. The first, who had chickens and ducks in their backyard, was hospitalized, while the second, who had visited a wet market with poultry present, only experienced mild symptoms. Both children recovered, and all close contacts were found to have tested negative for the virus.

Symptoms of H5N1 bird flu in humans have been previously found to vary widely in severity, from mild flu-like symptoms and conjunctivitis to severe acute respiratory issues, and, in some cases, death.

The WHO said it is looking into how this strain of the virus is related to other H3N8 viruses in both birds and other mammals, but its current thinking is that it cannot be spread between humans, only from other animals to humans.

"The available epidemiological and virological information suggests that avian influenza A(H3N8) viruses do not have the capacity for sustained transmission among humans. Therefore, the current assessment is that the likelihood of human-to-human spread is low," the WHO statement said.

The U.S. already has some degree of preparedness for defense against bird flu due to the current H5N1 outbreak, so the CDC advises to follow the same guidelines of minimizing exposure to birds by avoiding visits to poultry farms and bird markets, avoiding eating undercooked poultry products, and washing hands after any contact with birds or surfaces that may have been exposed to bird feces. Poultry farm workers are encouraged to wear protective equipment including goggles, gloves and masks.

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