A 2nd Michigan dairy farm worker has bird flu, CDC confirms. Here's what to know.

A Michigan dairy farm worker has become the third person in the United States — and the second in Michigan — this year to contract bird flu, also known as avian influenza, amid the latest outbreak among cattle, the Centers for Disease Control and Prevention confirmed on May 30. It’s the first of 2024’s three U.S. cases to involve typical flu-like symptoms, including cough. As with the other two human cases, CDC scientists believe this person contracted the virus from cattle, and there are no signs of bird flu spreading between humans. Health officials still consider the risk to the general public to be low, the CDC says. But the agency is stepping up precautions, especially for people in close contact with dairy cattle.

Here’s everything you need to know about the latest developments.

🇺🇸 How many people in the U.S. have been infected with bird flu?

Three this year, and four in total. Bird flu — which is technically a strain of influenza A, known to scientists as H5N1 — is widespread in wild birds and, to a lesser extent, poultry. In the U.S., the virus began spreading among poultry in 2022, when the first person contracted the virus while culling an infected flock in Colorado, according to the CDC. The virus began spreading for the first time among dairy cattle in the U.S. in 2024. A Texas dairy farm worker tested positive in April. Earlier this month a Michigan dairy farm worker was confirmed to have bird flu, followed by this latest case also involving a farm worker based in Michigan. The two infected people in Michigan worked at different farms, CDC officials said in a Thursday statement.

🌎 How many people have contracted bird flu worldwide?

Since 2003, there have been more than 880 human bird flu cases worldwide, according to the CDC. But they are still rare and “sporadic," occurring primarily in other countries. Until recently, the largest outbreaks have occurred as the result of exposures at poultry markets, which are common in certain countries including Egypt, China and Indonesia. But, since 2021, human cases of bird flu have begun cropping up in countries that had never had them before. Australia, for one, reported on May 22 its first-ever case of bird flu, in a child who was infected in March after traveling to India. The child’s infection was “severe,” but they have since recovered, according to Australian health officials.

🩺 How sick has bird flu made people?

All of the illnesses have been relatively mild. The only symptom of the first two infected people in Texas and Michigan, respectively, was pink eye (also known as conjunctivitis). The latest Michigan case is different, because the person developed respiratory symptoms — namely a cough. The farmworker was treated with an antiviral and is recovering in isolation at home. Fatigue was the only symptom reported by the American poultry worker infected in 2022. However, bird flu has led to severe infections and even 463 fatalities in other countries in the past, according to the World Health Organization.

🤔 Why is this happening now?

Viruses mutate constantly. But the latest bird flu mutations are somewhat worrisome. “This virus getting into cattle is relatively new and somewhat unexpected,” Dr. Arnold Monto, a University of Michigan professor of epidemiology who specializes in viruses, tells Yahoo Life. Bird flu becoming widespread among cattle means the virus has become better at infecting mammals, bringing it a step close to being able to infect humans easily. But, so far, the virus has only infected people in close, prolonged contact with dairy cattle.

😷 Should I be worried about catching bird flu?

Not unless you’re a dairy farm worker. There have been no instances of the virus spreading between people. And while more than 50 herds of dairy cattle have been infected, only two people have contracted bird flu in the U.S., out of the nation’s more than 100,000 dairy farm workers. However, the CDC has asked states to keep a close eye out for human infections. Officials on May 21 asked states to continue analyzing samples from people who test positive for flu throughout the summer, maintaining the level of surveillance that would be typical for the winter height of flu seasons.

🐮 Are dairy and beef safe?

Yes, experts say. Although fragments of bird flu have been found in some 20% of grocery store milk samples, these pieces of the virus cannot cause infection. So far, pasteurization — the standard sterilization process milk goes through — has proven very effective at inactivating bird flu in milk. Health officials have warned against drinking raw milk, however, which is unsterilized and can carry all manner of viruses and bacteria. Cooking ground beef to medium well or well-done temperatures also kills the virus.

This article was originally published on May 22, 2024 and has been updated.