2024 Bird Flu: What To Know About Current Risk To Humans

ACROSS AMERICA — The first U.S. case a highly virulent strain of bird flu spread from cattle to a human is raising questions about everything from humans’ susceptibility to the illness to the safety of the nation’s milk supply.

This is the second confirmed case of the H5N1 flu in a human in the United States, and the first linked to exposure to cattle, according to health officials. It comes as bird flu rates are on an uptick, with at least 29 states reporting they’ve had to cull more than 33 million domestic chickens.

An eye inflammation was the only symptom of the Texas patient, who originally was thought to have influenza. Health officials said the patient was being treated with the antiviral drug oseltamivir.

Most of the people who have gotten sick with bird flu infections got it directly from the birds. Texas officials didn’t release details about how the person came into contact with the cows.

Here are some things to know:

What’s The Risk To Humans?

Initial testing of the samples from sick cows didn’t have any genetic mutations that make the virus more likely to infect humans, the U.S. Department of Agriculture said in a statement last week.

“While cases among humans in direct contact with infected animals are possible, this indicates that the current risk to the public remains low,” the statement said.

More generally, some 460 people worldwide have died in the past decades from bird flu infections, according to the World Health Organization. The first time the threat to people was identified was in Hong Kong in 1997.

There have been no reported cases of person-to-person spread of the illness, according to the Centers for Disease Control and Prevention.

How Safe Is Milk?

There’s no reason for concern about the safety of the nation’s commercial milk supply because dairy products are pasteurized — a process that inactivates bacteria and viruses — before entering the market, the Food and Drug Administration said on its website Tuesday.

Also, the FDA said, only milk from healthy cows is authorized for distribution for human consumption. The milk from the infected cows won’t enter the food supply. The loss milk from the sick cows is so limited it is not expected to affect the price of milk or other dairy products.

However, the agency isn’t quite as confident when it comes to unpasteurized, or raw, milk, or cheese made from the raw milk of infected cows. Raw milk can’t be sold for human consumption on the commercial market, but it’s easy to find vendors who sell raw milk outside the regulatory system.

“Because of the limited information available about the possible transmission of [bird flu] viruses in raw milk, the FDA recommends that industry does not manufacture or sell raw milk or raw milk cheese products made with milk from cows showing symptoms of illness, including those infected with avian influenza viruses or exposed to those infected with avian influenza viruses,” the FDA said.

CDC data from 1998 to 2018 showed 2,645 illnesses and 228 hospitalizations linked to the consumption of raw milk.

FDA regulations require a 60-day aging process for unpasteurized cheese to ensure food safety, as the aging process is important to inactivate bacteria and viruses.

How Did Virus Jump To Cattle?

Cows from 12 dairy herds in five states — Texas (seven herds), Kansas (two herds), Idaho, Michigan and New Mexico (one herd each) — have tested positive for the virus, but some experts say it’s unlikely that’s the extent of infections. Until now, researchers had no reason to specifically look for bird flu infections in cattle.

“It could have been infecting dairy cattle a year ago. We just never thought about looking … for it,” David Swayne, an avian influenza expert who is now a private consultant after having worked for the USDA for 30 years, told Stat, a news organization covering medicine and the health industry.

Other mammals have been infected by bird flu. The USDA keeps a list of mammals that have been infected with bird flu, including big cats and domestic cats, brown bears and polar bears, raccoons, skunks, coyotes, mink and sea life like dolphins, sea lions and seals.

Carnivores in that group may have gotten it by eating the carcass of an infected bird, according to experts. Among dairy cattle and some other species, the likely route is through water or the grasses contaminated with virus shed by infected birds.

“There is massive (unprecedented) exposure of wild carnivores (feasting on sick/dead birds) and potentially also other mammals (through contaminated water and surface areas, including grasslands),” Ron Fouchier, an influenza virologist at Erasmus Medical Center in Rotterdam, the Netherlands, told Stat in an email. “The infected mammals get infected upon feeding/drinking, which is an alternative route of infection of mammals.”

Eggs Could Cost More

The largest U.S. egg producer, Cal-Maine Foods, has temporarily closed one of its Texas facilities after bird flu was found in chickens and culled about 1.6 million hens and 337,000 pullets — about 3.6 percent of the company’s flock, which was infected with the same strain that caused the dairy worker to become ill.

Cal-Maine, which controls 20 percent of the U.S. egg market, said it is “working to secure production from other facilities to minimize disruption to its customers.”

If egg producers aren’t able to keep up with demand, or if bird flu infects more flocks, egg prices could go up from the current level, about $3 a dozen. They have been inching up for months, from $2 in the fall and are at the highest level since April 2023, according to the Labor Department’s Consumer Price Index.

When egg prices hit a record $4.82 for a dozen in January 2023 following the last widespread bird flu epidemic, Cal-Maine saw its revenue double and profit surge 718 percent, CNN reported.