An outbreak of avian flu at a Spanish mink farm in October 2022 and several other reported cases of the virus's spread to mammals sparked concern of its transmission to humans. But experts say it will take a lot for avian flu to become a full-fledged human pandemic, Science reported.
Human cases of avian flu are deadly, but historically rare, according to the CDC. A few have cropped up across the globe in places like China, Cambodia and Chile throughout the past year, but largely from direct contact with infected birds or animals — not from human-to-human transmission.
The H5N1 strain of avian flu has been the one responsible for a majority of human cases to date, but for the flu to become a full-scale, concerning human pandemic, experts say a few key things must happen first:
- Several of the strain's proteins must evolve to "become adept at spreading between mammals," Science reported.
- The strain must undergo significant "changes in hemagglutinin," which would allow it to better attach to host cells.
- The hemagglutinin must also experience a "a pH-dependent shape change" after attaching to a cell and being transported to a vesicle that is more acidic, which would allow it to be more easily transmissible via air.
- The virus may also need to evolve and become able to "evade an intracellular protein called MxA," which alerts the body's immune system of influenza.
"With the virus spreading so furiously around the globe, it has more opportunities to hit the right combination than ever before," according to Science. "In the past, H5N1 outbreaks have faded, but this time, the virus is probably here to stay in wild birds in Europe and the Americas."