H3N8 bird flu claims its first human with the death of a woman in China

A 56-year-old woman in China has died after contracting H3N8 bird flu, the first known fatality in a human from this strain of avian influenza. 

While H3N8 is “one of the most frequently found” subtypes of flu found in birds, the woman is only the third person known to have caught the virus and the first to have died.

Two young boys were infected with the same virus in unrelated cases in China last year, but both survived. 

According to a World Health Organization report, the woman developed symptoms in late February and died on March 16. She had “multiple underlying conditions” and is thought to have caught the virus at a wet market, where scientists tracing her exposure collected samples positive for H3N8. 

The infection is unrelated to the H5N1 bird flu pandemic that has devastated poultry and wild bird populations around the world in the last 18 months and has spread to mammals including foxes, sea lions and even domestic cats.

There is also no evidence the H3N8 can be spread person to person. “No close contacts of the case developed an infection or symptoms of illness at the time of reporting,” said the WHO.

While H3N8 is less dangerous for both wild birds and domestic poultry than H5N1, “causing minimal to no sign of disease”, it has also been detected in various mammals before – including horses and dogs. 

In 2011, there was an outbreak of H3N8 among harbour seals in New England, US that killed 162 animals. 

There are many types of avian influenza, with the viruses described by two different proteins – hemagglutinin and neuraminidase (the H and N in the naming sequence). To date, scientists have identified 18 different subtypes of the former, and 11 of the latter, in circulation.

Just six of these (H5, H6, H7, H8, H9, and H10 viruses) have so far infected humans, with H5N1 and H7N9 responsible for the bulk of known cases. 

“H3N8 viruses were first detected in wild birds in the 1960s and have been detected in other animals,” the US CDC said in a statement on Monday. “Avian influenza H3N8 viruses have been sporadically detected in poultry in China and some have been found to be genetically closely related to the human cases reported in 2022”.

For now, the H5N1 bird flu pandemic remains the greater concern as regards the risk to humans.

The sheer number of cases in birds and increasing transmission in (and potentially between) mammals – including mink, otters and even pet cats – increases the opportunity for the virus to mutate and become able to spread between people.

“If transmission between mammals have started, the virus has changed and this could increase the risk for human health,” Dr Pablo Plaza, an expert in veterinary public health and epidemiology at the National University of Comahue in Argentina, and co-author of the first pre-print describing the sea lion outbreak in Peru, told the Telegraph earlier this year.

“Until now, this risk seems to be low – however, we must be alert since [the] virus is changing all the time. Several changes in the virus are needed to adapt to human-human transmission, so hopefully they will not occur,” he added.

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