What to know about bird flu

• Outbreaks, which spread rapidly and can cause significant illness and death among poultry, can have major agricultural and economic implications and in rase instances can be transmitted to humans.
• A new analysis of genetic data indicated the latest outbreak in U.S. dairy cows may have started in December or January – earlier than previously thought, per the New York Times.
• The Biden administration said this week it will require that all dairy cows receive negative flu tests before they can be transported over state lines.

What is bird flu?

Bird flu is a disease caused by infection with avian influenza Type A viruses, per the Centers for Disease Control and Prevention.

• The viruses are very contagious among birds, and can sicken and kill certain domesticated bird species, including chickens, ducks and turkeys.

How does bird flu spread?

It spreads globally among susceptible birds through contact as an infected bird sheds the virus in its saliva, nasal secretions and feces, according to the CDC.

• Infections can also occur via contact with contaminated surfaces.

Which animals are most susceptible?

The viruses normally spread among birds, according to the World Health Organization.

Yes, but: An increasing number of aviation flu cases among mammals, including cattle, "raises concern that the virus might adapt to infect humans more easily," the WHO says.

• Last month, the American Veterinary Medical Association said a goat in Minnesota had become the first domestic ruminant to test positive for bird flu in the U.S.

What threat does bird flu pose to humans?

While human infection is possible, its occurrence is rare.

• People with close or prolonged, unprotected exposures to infected birds or other animals or to contaminated environments face greater risk of infection.

Threat level: A person in Texas was being treated for the H5N1 strain of the flu after exposure to dairy cattle presumed to be infected with the virus, health officials said Monday.

• The infection doesn't affect the CDC's current health risk assessment for the public, which is considered low.

• This case is only the second human case of H5N1 in the U.S., CDC data show. The first was reported in Colorado in 2022 after the patient was exposed to poultry.

Do outbreaks impact cow milk supply?

The Food and Drug Administration reported April 23 that trace amounts of the bird flu had been detected in pasteurized milk samples taken from grocery store shelves.

• "Based on information currently available, our commercial milk supply is safe," Donald Prater, acting director of the FDA's Center for Food Safety and Applied Nutrition, told reporters.
• Although small amounts were found in pasteurized milk, the pasteurization process is typically key in weeding out contamination.

In March, bird flu was detected in unpasteurized milk samples and swabs from dairy herds in Texas, Kansas and Michigan.

• But federal authorities said there was "no concern" about the safety of the U.S. milk supply.
• Still, the FDA recommends that people avoid unpasteurized (raw) milk and cheese products.

Worth noting: The bird flu outbreak has contributed to rising egg prices.

• Cal-Maine Foods, the biggest egg producer in the U.S., said on April 2 that it halted production at a Texas facility after some of its chickens tested positive, leading it to cull about 3.6% of the company's total flock.

Go deeper: Person in Texas contracted bird flu after exposure to infected cows