Concerns grow as ‘gigantic’ bird flu outbreak runs rampant in US dairy herds

Bird flu has already spread to wild birds, chickens and mammals, including a polar bear and an alpaca. The more widespread it becomes, the more officials worry it could spread among people.

USA TODAY

More than three years into a worldwide outbreak of bird flu, the virus continues to expand in the U.S., with growing impacts to food production and animals. Over 80 million chickens, thousands of wild birds and dozens of mammal species, including a polar bear, have been infected.

Now it’s running rampant among dairy cows, turning up in 94 herds across 12 states since March. The latest animal to test positive was an alpaca on an Idaho farm.

‘It’s gigantic, the scope and scale of the presence of the disease,’ said Julianna Lenoch, national coordinator for the Department of Agriculture’s wildlife disease program.

This scale ‒ and related concerns ‒ are reflected in the price of eggs, renewed warnings to cook ground beef and eggs thoroughly, and in extraordinary measures dairy and poultry farmers are being asked to take to prevent its spread.

As the outbreak lingers and expands, it’s prompting growing concerns about the risks to humans and the influence of warmer temperatures and more extreme weather events in making this and future pandemics worse.

How widespread is this bird flu outbreak?

The highly contagious H5N1 virus has spread to six continents since the first detections in Europe and Asia in 2020. It has been reported across North and Central America and most of South America and has been found on every continent except Australia. It also turned up in Antarctica last fall.

The U.S. has experienced avian influenza outbreaks in the past, but this one is lasting longer and is more widespread. Domestic poultry flocks, either in commercial operations or backyard flocks and farms, have been infected in every state except Louisiana and Hawaii, including more than 5.9 million birds just since May 1.

Since 2022, infections have been reported in 14 million turkeys and 80 million chickens, including 71 million egg layers. Farmers must kill chickens and turkeys when a poultry flock tests positive, and experts say the slaughter to prevent human infection has helped drive up the cost of eggs.

Infected mammals have been found in 31 states, with the greatest number of infections found in foxes, mice, striped skunks, mountain lions, cats and harbor seals.

Research studies find the prolonged presence and spread of the virus increases the risk of genetic mutations that could allow it to pass more easily from animals to people and among people.

‘The longer we have virus out there, the more possibility there is for changes,’ said Lenoch, who oversees the federal program responsible for tracking the virus in wild birds.

Can humans get bird flu? 

Since it arrived during the winter of 2021-2022, four people have tested positive in the U.S. All were exposed to the virus on farms. In the first case, in 2022, the worker was helping to cull infected poultry on a farm. All three patients this year had exposure to dairy cows. Two only reported conjunctivitis, or pink eye, while the third also experienced upper respiratory symptoms. No one in the U.S. has died from the virus, according to federal officials, but deaths have been reported internationally.

So far, for the general public, everything but raw milk is considered safe, federal officials say, as long as you’re cooking ground beef and eggs all the way through. Cooking takes care of any remnants of the virus that could be in egg yolks or in ground beef after once-infected dairy cows are shipped to market to be butchered.

In milk, pasteurization kills the active virus so it can’t be transmitted, federal research shows. However, traces of the virus remain, and are found in an estimated 20% of the nation’s milk supply.

The Food and Drug Administration said it does not know if the virus can be transmitted in raw milk, but has asked states that allow the sale of raw milk to restrict it as a precautionary measure.

‘The fact that it’s in 20% of our milk supply should be disturbing to everyone because that means it’s gone around already,’ said Xavier Becerra, U.S. Health and Humans Services secretary, during a speech to the Western Governors Association last week. ‘If it starts to jump, that’s when we really have to worry.’

Why are officials concerned about human exposure to bird flu?

The great concern among federal agencies and researchers is that the virus will evolve and become more contagious among humans. For now, it’s hard for humans to contract the virus and it hasn’t been passed from person to person.

Without stringent measures to avoid repeated viral transmission between wild and domestic animals, experts say the risks to people will grow.

The Department of Agriculture and Centers for Disease Control and Prevention are urging farmers to step up efforts to prevent the spread by cleaning and disinfecting equipment, especially when the same equipment is used to handle manure and feed and to better protect farm employees.

Preventing farm to farm spread is ‘really critical,’ agency officials said Thursday.

How is this outbreak of avian flu different from previous ones?

The outbreak is ‘unique in global expansion’ and in the number of bird and mammal species that it’s infecting, concluded a study published earlier this year by Tufts University researchers Jonathan Runstadler and Wendy Puryear.  ‘Though the risk to humans remains low, this unexpected outbreak illustrates the continued need for vigilance and further study,’ the study stated.

Avian influenza is spread globally among birds, particularly migratory waterfowl such as ducks. They’re natural reservoirs and migrate over long distances, traversing hemispheres in some cases. As they travel, infected birds shed the virus in mucus, saliva, and feces.

In previous outbreaks, wild birds would often get exposed and just carry the virus around with no symptoms, Lenoch said. With the current strain that has evolved however, wild birds are getting sick and dying in large groups.

The virus raises many concerns, not only because of its impacts on human health and agriculture, but also because it’s killing wildlife, such as seabirds, raptors and marine mammals, said Diann Prosser, a research wildlife biologist with the U.S. Geological Survey’s Eastern Ecological Science Center.

The spillover into dairy cows is extremely rare and officials aren’t certain how it started. One study released by federal officials this week said it likely started with wild birds infecting a singular cow in the Texas Panhandle. Cows from that herd, which weren’t showing any symptoms at the time were shipped to Michigan, where the virus quickly spread to other states. Investigations continue.

Typically, outbreaks eventually burn themselves out as wild birds build immunity and stop spreading the virus. That’s expected to occur this time, as well, but it’s taking longer than usual.