Avian influenza spread: WHO gives public health warning as FDA calms food safety concerns

23 Apr 2024 --- The World Health Organization (WHO) has warned that the ongoing spread of avian influenza poses a “significant public health concern” and urged health authorities, especially in the US, to closely monitor infections in cows. However, the US FDA maintains that the virus is not currently a concern to consumer health and downplayed its impact on commercial milk production. 

Earlier this month, the largest producer of fresh eggs in the US halted production at a Texas plant after bird flu was detected in its chickens. Cal-Maine Foods said that about 3.6% of its total flock was destroyed after the infection.

However, the virus, also known as H5N1, has now been found in at least 26 dairy herds across eight US states, marking the first time this strain of bird flu has been detected in cattle, according to officials.

At least 21 states have restricted cattle importations from states where the virus is known to have infected dairy cows.

The US Department of Agriculture’s Animal and Plant Health Inspection Service strongly recommends minimizing the movement of cattle, but has not issued federal quarantine orders.

Public health threat
The US Centers for Disease Control and Prevention (CDC) confirmed this month that a dairy worker in Texas, who reportedly had exposure to dairy cattle presumed to have had avian influenza, contracted the virus and is now recovering.

“This infection does not change the H5N1 bird flu human health risk assessment for the US general public, which CDC considers to be low,” the agency said in a press release, while acknowledging that people who come into more frequent contact with possibly infected birds or other mammals have a higher risk.

Meanwhile, WHO’s chief scientist, Dr. Jeremy Farrar, told reporters recently in Geneva, Switzerland, that H5N1 has had an “extremely high” mortality rate among the several hundred people known to have been infected with it to date.

US health officials have downplayed the impact of bird flu on food safety and industry production.However, no human-to-human H5N1 transmission has yet been recorded.

“H5N1 is an influenza infection, predominantly started in poultry and ducks and has spread effectively over the course of the last one or two years to become a global zoonotic — animal — pandemic,” said Farrar. 

“The great concern, of course, is that in doing so and infecting ducks and chickens — but now increasingly mammals — the virus now evolves and develops the ability to infect humans. 

“And then critically, the ability to go from human-to-human transmission.”

Concerns with cattle
US health officials have stressed that bird flu’s risk to the public is low, and the country’s food supply remains safe and stable.

“At this time, there continues to be no concern that this circumstance poses a risk to consumer health or that it affects the safety of the interstate commercial milk supply,” the FDA said in a statement.

According to officials, farmers are being urged to test cows that show symptoms of infection and separate them from the herd, where they usually recover within two weeks.

US producers are not permitted to sell milk from sick cows, while milk sold across state lines must be pasteurized or heat-treated to kill viruses, including influenza.A dairy worker in Texas reportedly contracted the virus after exposure to cattle.

“We firmly believe that pasteurization provides a safe milk supply,” Tracey Forfa, director of the FDA’s Center for Veterinary Medicine, told a webinar audience last week.

However, WHO’s Farrar has urged further caution by public health authorities “because it [the virus] may evolve into transmitting in different ways.”

“Do the milking structures of cows create aerosols? Is it the environment which they’re living in? Is it the transport system that is spreading this around the country?” he said.

“This is a huge concern, and I think we have to…make sure that if H5N1 did come across to humans with human-to-human transmission that we were in a position to immediately respond with access equitably to vaccines, therapeutics and diagnostics.”

According to a new European Food Safety Authority report, outbreaks of avian influenza continue to spread in the EU and beyond.

By Joshua Poole