New Human Cases of Avian Flu Anticipated
Allison Shelley
June 19, 2024
25
253
With avian influenza spreading quickly around the globe, the virus has more opportunities to mutate and cause problems for people. By some calculations, H5N1 bird flu is still at least two mutations away from widespread human infections, but experts warn that new flu symptoms in individuals at high risk are likely to start turning up in health systems this summer.
"There is a broad range of symptoms to be watching for," said Vivien Dugan, PhD, director of the influenza division at the US Centers for Disease Control and Prevention (CDC). "Some of this will not be obvious or at the forefront of our minds."
Dugan is leading the team of CDC scientists that is working with partners from the US Department of Agriculture, the US Food and Drug Administration (FDA), and state and local health departments to track and respond to the H5N1 bird flu outbreak currently sweeping through the US.
Since 2022, avian influenza A viruses have been detected in more than 9300 wild birds in 50 states and territories and in commercial and backyard flocks.
"It's a bad situation," said Florian Krammer, PhD, professor of vaccinology at the Icahn School of Medicine at Mount Sinai in New York. "Globally, we've seen tons of exposure in cities around the world and even in the birds here in New York City where I am."
Birds shed the virus in their saliva, mucous, and feces, so people or other animals with close, unprotected contact with infected birds or their contaminated environments can be infected.
And for the first time in March 2024, H5N1 bird flu was reported in dairy cows. The US Department of Agriculture said that at last count 101 dairy herds in 12 states had been infected, with several cases also found in dairy workers.
From Birds to Cattle and Farm Workers
The National Veterinary Services Laboratories confirmed the infections were highly pathogenic avian influenza H5N1 clade 2.3.4.4b of Eurasian lineage. Also known as the goose, Guangdong clade from China, phylogenetic analysis and epidemiology suggests a single introduction into cows followed by onward transmission.
"I was surprised when H5 was introduced to dairy cattle in this way," Dugan said during an interview. "Influenza viruses are always surprising us and it reminds me to stay humble and keep an open mind when dealing with them."
