Avian flu: Where did it come from, and how can it be stopped?

As of this week, highly pathogenic avian influenza has been found in 24 states and has resulted in the death of 23 million birds.

Highly pathogenic avian influenza has affected more than 1 million birds at more than 20 sites in Minnesota as of the first week of April 2022.
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ST. PAUL — Minnesota poultry farms are being hit by an outbreak of highly pathogenic avian influenza that has already affected more than 1 million birds at more than 20 sites across the state.

As of this week, 23 million birds have been affected in 24 states in the worst avian influenza outbreak in U.S. poultry flocks since 2015. Here’s what we know so far:

What is HPAI?

Highly pathogenic avian influenza — or HPAI — is caused by a highly contagious virus that is generally lethal to domesticated birds. There are other strains of avian influenza that are considered low pathogenic where birds either show mild signs of illness or none at all. Once exposed to infection, birds die within about 48 hours, according to Beth Thompson, state veterinarian and executive director of the Minnesota Board of Animal Health.

The virus is of particular concern in Minnesota, as the state is the top turkey producer in the U.S. Each year, producers raise about 40 million birds . In the 2015 outbreak farmers lost millions, and nationally the federal government response cost billions of dollars.

Thompson said the H5N1 influenza virus currently affecting U.S. flocks was present in Europe more than a year ago. It eventually spread to North America, where migratory birds have been spreading it to poultry operations across the U.S. and Canada.


During the 2015 outbreak, 23 counties and more than 100 farms were affected by the virus. While it’s too early to say how severe the current outbreak could become, as of Thursday officials had confirmed the virus’s presence in about a dozen Minnesota counties.

As of this week, it is affecting about half of the states in the U.S. and has resulted in the death of 23 million birds in states including Iowa and Wyoming. Thompson said the current outbreak already appears much more widespread than the one in 2015 when more than 50 million birds died of disease or were euthanized.

To date, the avian influenza has been detected in 21 Minnesota flocks, affecting 1 million birds.


The current outbreak of avian influenza virus is being spread by migrating birds, which can be infected without appearing sick. Geese and ducks are on the move as winter ends, and when they land, they can leave fecal matter containing the virus. Avian influenza is so contagious that small amounts of contamination on a farmer's boots could trigger an outbreak in a coop.

"The lakes are starting to open up, the ponds are starting to open up," Thompson said. "All it takes is just a little bit of that fecal matter, and it could be as something as simple as walking through a puddle."

There are multiple migratory corridors in the continental U.S. including the East Coast wild waterfowl pathway, one that comes up the Mississippi River, and one just west of Minnesota known as the Central Flyway. There is also a west coast pathway called the Pacific Flyway. The virus is present in all of them, Thompson said.

How this outbreak plays out depends on many factors, but warmer weather could be a big help.

"We need the sunshine. We need summer to come, we need the environment to dry out we need the environment to warm up and we need the wild waterfowl and migratory birds to complete their path up to their northern nesting grounds so they stop flying over the state," Thompson said. "As soon as we can get into some warmer weather I think we'll be moving in a better direction."


Stopping the spread

When HPAI is identified in the flock, the standard procedure is to euthanize all the birds in order to prevent the virus from spreading more. The virus is extremely lethal to domesticated birds, and most will die shortly after infections are identified.

The standard procedure for “depopulating” a coop is to use a machine that spreads foam over the birds and prevents them from breathing. Thompson said the practice is in accordance with guidelines from the American Veterinary Medical Association.

Farmers can take biosecurity measures to prevent their flocks from getting infected. University of Minnesota Extension poultry educator Abby Schuft said federal officials require larger operations to have a biosecurity plan in place that gets audited by state authorities every two years.

"The USDA spent billions of dollars in 2015 with depopulating birds and the recovery of those commercial flocks and they decided they didn't want to do that again,” she explained.

Many of the steps to prevent the spread are fairly simple. Wearing clean boots when entering a coop and ensuring hands are clean before handling birds are two central rules. It also helps to make farming spaces unattractive to migratory birds by eliminating puddles and ponds and not leaving feed out in the open. Some who raise chickens in urban areas like to leave grain strewn about their yards to allow their chickens to roam and graze, but this can attract unwanted visitors who may bring infection, Schuft said.

Can humans get HPAI?

Public health officials closely monitor farmers and crews sent out to eliminate infected flocks for signs of animal to human transmission of the virus, Schuft said. So far there have been no reports of the current H5N1 strain infecting humans.

Avian influenza viruses rarely infect humans, according to the Centers for Disease Control and Prevention. Animal to human infections typically happen when humans have unprotected contact with infected birds or virus-contaminated surfaces. It is even rarer for a human infected with avian influenza to spread the virus to another human.

Federal agriculture officials say it is not possible to get avian influenza from eating poultry or eggs. The chances of infected poultry entering the food supply are extremely low , as birds are typically destroyed.

Alex Derosier covers Minnesota breaking news and state government for Forum News Service.
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