The latest on bird flu: Another dairy farm worker infected, calls for testing and more

The latest updates on bird flu. (Getty Images)

A second dairy farm worker — this time in Michigan — has contracted bird flu in the United States this year, the Centers for Disease Control and Prevention confirmed in a May 22 press statement. In April the CDC confirmed the first human case of the year, a dairy farm worker infected in Texas. Both infected individuals had prolonged close contact with infected cattle and only experienced pink eye as a symptom. The CDC maintains that the risk to the general public is "low."

Dairy cattle herds have been infected in Texas, Colorado, Idaho, Kansas, Michigan, New Mexico, North Carolina, Ohio and South Dakota. Cases in birds in New York City parks and green spaces have also been confirmed by Icahn School of Medicine at Mount Sinai researchers.

How concerned should you be about bird flu, and what might this mean for the food supply? Here’s what you need to know.

🩺 What is bird flu?

Bird flu — clinically known as influenza A (H5N1) — is a variation of flu virus that spreads primarily among birds and poultry and can be highly contagious and even fatal among birds, according to the CDC. Occasionally, the virus will jump to other animals if they eat infected birds or drink water contaminated by the feces of infected birds, the CDC says. That has become more common in recent years. Viruses are constantly mutating, and the more they spread, the more they mutate. A recent family of variants may be particularly adept at infecting other animals, including cattle, according to the World Health Organization.

It’s rare for the virus to infect humans, and when it does happen, it’s usually confined to one person who was in close contact with an infected animal and doesn’t spread to others. Bird flu may cause mild to severe sickness in humans, and it has the potential to cause pneumonia and severe, sometimes fatal lung inflammation. Since 2020, there have been 26 cases in humans confirmed by the WHO, seven of which have been fatal.

❓Have people been infected?

Two people have been infected in this year's outbreak among dairy cattle, making a total of three people in the U.S. who have had the virus ever. (The first-ever U.S. case was in a poultry worker who contracted the virus in 2022 while culling infected birds and recovered after experiencing only mild fatigue.)

The Michigan dairy farm worker was being closely monitored after coming into contact with infected dairy cattle. Their only symptom was pink eye, and they initially tested negative for H5N1 when their nose was swabbed. However, an eye swab confirmed that they had bird flu. They have since made a full recovery.

The first human case of 2024 (and second case ever) detected in the U.S. was a dairy farm worker in Texas, who was diagnosed in late March after developing pink eye. Eye inflammation was the only symptom the Texas dairy worker experienced; they never developed any respiratory symptoms that health officials might have expected with bird flu.

🧑‍🔬 What's being done?

The federal government is providing $200 million to help stem transmission, Reuters reported on May 10. The CDC has also requested that states provide personal protective equipment (PPE) to dairy farm workers who might be at risk, according to an emailed statement. Federal funding will provide each affected farm with up to $28,000 a day toward measures to slow the spread among animals and prevent transmission to humans, CNN reported. Health agencies will also get $101 million for continued food safety monitoring.

Dairy and poultry farmworkers remain the CDC's main concern. On May 6, the agency asked state health and agriculture departments to provide PPE to dairy farm workers at risk of contracting bird flu in an effort to prevent any additional cases, the agency said in an emailed statement. The agency has also asked state health officials to take other steps like making sure they have bird flu tests available to confirm possible infections. It also said health officials should stay in close contact with veterinarians and agriculture department officials and asked to be notified of any "challenges" states encounter.

🏥 What are the risks to humans?

For the general public, the risk remains low, the CDC says. Although human bird flu cases are extremely rare in the U.S., the CDC has asked states to step up their monitoring for the virus. Summer brings a lull in cases of common human flu, so testing often falls off. But, on May 21, the CDC said states should keep their monitoring at peak levels, testing positive flu samples to see if the illness was caused by H5N1.

🥛 What does it mean for our food and milk?

After particles of the bird flu virus were discovered in about 1 in 5 samples of grocery store milk, further Food and Drug Administration testing has confirmed that the virus was inactivated by pasteurization, a sterilizing process used on more than 99% of the commercial milk supply. The U.S. Department of Agriculture also tested ground beef for bird flu, and all the samples came back negative.

Bird flu has also been found in unpasteurized milk, but you shouldn’t consume unpasteurized milk or cheese regardless, the CDC warns, because they carry risk of infections like listeria. The CDC also says that the risk of being infected from eating eggs is low, and properly cooking them would kill any virus anyway.

Farms are prohibited from selling products — including milk and eggs — from sick animals, so it’s unlikely that contaminated food would wind up on grocery store shelves. The most likely impact of the bird flu outbreak in animals on the food supply is rising prices. Egg prices have shot up as chickens have been culled or died, limiting the supply of eggs. Milk prices could see increases but are stable so far.

On April 15, Colombia became the first country to restrict the importation of beef and beef products from U.S. states with infected herds, Reuters reported.

💉 Are there bird flu vaccines and treatments?

Two candidate vaccines — drafts of what would become the shots — seem to be good matches for the current strain of bird flu, the Washington Post reports. The federal government has a stockpile of enough doses to vaccinate a fifth of the American population, officials told Barron's. However, the vaccines are undergoing clinical testing, so it's unclear how effective they will be. Antiviral drugs can also be used to treat bird flu, although the CDC says that some variations of bird flu first found in Asia aren’t as responsive to these treatments.

Dr. Arnold Monto, a professor emeritus of epidemiology at the University of Michigan and member of the FDA’s vaccine committee, tells Yahoo Life that the U.S.’s bird flu vaccines require adjuvants, ingredients that improve human’s immune responses. An official with the Department of Health and Human Services also told the Washington Post that components for the vaccines are being tested, and it would likely take weeks to months for them to be ready for widespread distribution. Monto adds that the vaccine would also likely be given to only those at high risk — poultry and dairy farmworkers — since there’s no evidence that bird flu spreads among humans.

🙅 How can I avoid bird flu?

Avoid close or prolonged contact with wild birds, cattle or any other animal suspected of being infected. The CDC also recommends steering clear of surfaces that may be contaminated with raw milk, animal feces, litter or anything else that might have crossed paths with an infected animal.

Cooking poultry and eggs to an internal temperature of 165˚F will kill off any virus. It's also recommended for milk drinkers to consume only pasteurized milk to prevent contracting bird flu or other viruses or bacteria from raw foods, and to avoid raw or undercooked foods sourced from animals that may be infected with bird flu.

This article was originally published on April 4, 2024. It has since been updated.