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Bird flu has been spreading among domestic and wild birds in the U.S. Viara Mileva/Getty Images
  • Dairy cows in Minnesota have been diagnosed with avian flu, according to state officials. They are the first cattle to develop the disease in that state.
  • Two dairy workers in Michigan have been diagnosed with H5N1 bird flu after exposure to cattle presumed to be infected with the virus.
  • In total, three people have been diagnosed with H5N1 bird flu in recent months and the second person to be in Michigan to develop the disease.
  • The risk to the general public remains low, because there is no sign of person-to-person transmission of the virus.

Minnesota officials announced that cows in a dairy herd have been diagnosed with the H1N1 strain of avian flu.

The Minnesota Board of Animals reported that about 40 animals in a dairy herd had symptoms consistent with avian flu. Samples from the animals were then sent to the USDA’s National Veterinary Services Laboratories, which then confirmed the animals had developed avian flu.

“We knew it was only a matter of time before this detection would reach our doorstep,” said Minnesota State Veterinarian, Dr. Brian Hoefs in a statement. “It’s important for dairy farmers to follow the example of this herd and test sick cows. The more the animal health community can learn about this virus today through testing and research, the better we can equip ourselves to prevent infections tomorrow.”

The board said that dairy farmers should be vigilant for signs of avian flu in cattle but reiterated that the risk to humans remains low.

The news comes after two dairy workers in Michigan were recently diagnosed with bird flu. In total there have been three confirmed human cases related to infected cattle since the virus was first detected in dairy cows in late March.

The risk to the general public remains low, the Centers for Disease Control and Prevention (CDC) said in a statement, although it continues to recommend precautions for people who are exposed to infected or potentially infected animals.

The CDC told reporters on a call in May that there is no evidence that the virus is spreading from person to person, Reuters reported. Since March, the agency has tested close to 40 people who had exposures on a dairy farm or were connected to a farm, Reuters said.

Genetic tests carried out by the CDC on samples from the patient in Texas and infected cattle show that the virus lacks changes that would make it better able to infect mammals. There is also no sign that the virus has developed resistance to antiviral treatments, the CDC said.

In late March, dairy cows in Kansas and Texas tested positive for bird flu. Since then, the outbreak has spread to additional herds in New Mexico and Ohio.

Federal agriculture officials emphasized that the food supply remains safe. Milk from sick cows is diverted or destroyed, and pasteurization kills any viruses or bacteria in milk.

The bird flu cases in Texas and Michigan are the first linked to exposure to cattle, federal health officials said.

The only other human case of bird flu in the United States occurred in Colorado in 2022, in a person who had contact with infected poultry.

Bird flu is a disease caused by an influenza virus that mainly infects birds.

These types of viruses, known as avian influenza A viruses, spread naturally among wild aquatic birds such as ducks and geese. From there, they can pass to chickens and other domesticated poultry.

There are two groups of these viruses: low pathogenic avian influenza (LPAI) and highly pathogenic avian influenza (HPAI).

The second group causes severe disease and high death rates in infected birds. This group includes the highly pathogenic avian influenza A (H5N1) virus — aka H5N1 bird flu — detected in cattle and the patient in Texas.

Certain bird flu viruses can spread to and infect mammals, including seals, bears, foxes, skunks, domestic cats and dogs, and humans.

“People who are at risk are those who have direct and prolonged exposure with infected, ill or dead animals, or areas contaminated by infected birds or animals,” said Dean Blumberg, MD, chief of pediatric infectious diseases at UC Davis Children’s Hospital.

It is rare for bird flu viruses to spread from an infected person to another person, but it has happened. In these cases, the virus has spread to only a few people, and often within a person’s household, where there is prolonged, close contact.

“Human-to-human transmission is extraordinarily rare,” Blumberg told Healthline, “and in fact there is no risk of sustained human-to-human transmission, so this [virus] poses no threat to the general public.”

The federal government maintains a stockpile of vaccines, including ones that target H5N1 and H7N9 bird flu viruses. These could be mobilized if there are signs of human-to-human spread of the virus.

However, Blumberg said the chance of that happening right now is low.

“It would be concerning if avian influenza evolved to be more easily transmitted among people, since [we have] little to no immunity to this virus,” he said. “However this has not happened since bird flu was first described almost 150 years ago.”

Symptoms of bird flu in people range from mild to severe, and may include:

  • eye redness
  • flu-like upper respiratory symptoms such as cough, sore throat, runny or stuffy nose
  • pneumonia
  • fever
  • muscle or body aches
  • headaches
  • fatigue
  • difficulty breathing or shortness of breath

As of December 2023, 902 people have been infected with avian influenza H5N1 virus worldwide in 23 countries, reports the CDC. More than 50% of people died as a result of their infection.

However, the severity of the cases varied depending upon the genetic characteristics of the virus involved, ranging from causing no symptoms to leading to severe illness and death.

With only two human cases in the recent outbreak associated with dairy cattle, it is too soon to know if all cases will be mild. Health officials are closely watching the situation.

To protect yourself and your pets from bird flu, the CDC recommends:

  • Avoid direct contact with wild birds, or with wild or domestic birds that appear sick or have died.
  • Avoid unprotected exposure to infected live or dead animals, including cattle, domestic pets, and other mammals.
  • To move or discard a dead bird or other animal, don’t touch it with your bare hands. Use gloves or a plastic bag to place the body inside a garbage bag.
  • Wash your hands with soap and water after exposure to wild birds or other animals, as well as domesticated farm animals.

If you find a dead bird, check with your state health department, state veterinary diagnostic laboratory, or state wildlife agency to find out how to report it.

In addition, “for those who work in the [animal] industry and do have contact with potentially infectious animals and environments, full personal protective equipment) should be used including goggles, N95 or equivalent, gown, gloves, hair and boot covers,” said Blumberg.

The CDC also recommends that you get a seasonal flu vaccine. This won’t protect you from bird flu, but will reduce your risk of getting seasonal flu and bird flu at the same time.

At least 40 cows in a herd of dairy cattle in Minnesota have been diagnosed with the H1N1 version of avian flu. They are the first cattle in the state to develop the disease.