In the U.S. alone, the H5N1 avian flu strain has killed nearly 58 million birds in the last year. While the virus currently poses a low risk to humans, experts are concerned about its pandemic potential if it were to make a sustained jump.
Globally, there have been 868 cases of human infection with H5N1 since January 2003, according to recent data from the World Health Organization. The cases are tied to the handling of infected poultry. Experts say the overall risk to humans remains low, but as the virus continues to infect more people, the chances of it adapting mutations that would enable it to spread from person to person grow.
"There is concern about it having pandemic potential," Wendy Blay Puryear, PhD, a molecular virologist at Tufts University in Medford, Mass., told The Guardian in a Jan. 12 report. "Before COVID-19 was on anybody’s radar, this was the one that we were all watching very closely."
The disease is highly fatal among humans. Of the 868 global cases reported since 2003, 457 were fatal — a 53 percent case-fatality rate.
The potential for bird flu to make a leap to humans is essentially a numbers game, Dr. Ian Barr, deputy director of the WHO's collaborating center for reference and research on influenza, told The Guardian.
"The more viruses that are out there, the more species that they infect, the longer they hang around for, then the more chance there is for something to mutate or go awry or reassort with an unwanted consequence," he said.
However, it is a good sign for public health that H5N1 outbreaks among birds have gone on for years without sustained human transmission, experts say.
"We never really know with these viruses. … But they’ve been with us for 18 years in various forms and they haven't yet gained that function of being easily transmissible to man," Dr. Barr said. "So hopefully the virus finds that a difficult thing to do, but it's something which we're not entirely knowledgeable about."