Terrell Harmon casts a wary eye overhead as two of his family’s Plymouth Rock Blues peck at clumps of mulch in their expanding vegetable garden.

Harmon’s not an alarmist, but this year he and his wife, Alex, have reason to worry about wild birds flying over their property.

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The highly pathogenic avian influenza is affecting a larger number of wild birds this year. A single dropping in the yard could infect their hens, which besides producing the family’s eggs, are also all pets.

“I have a map I check every so often,” says Alex Harmon, a counselor at Snowden School . “If the outbreaks start getting closer, we will restrict them more.”

While wild birds carry avian flu, they generally don’t get as sick as domestic flocks. But this year, there are widespread reports of raptors dying of H5N1, the virus detected early in the migrating season this year among birds in eastern Canada.

In the last several days, more than 1.7 million birds have been killed in two massive outbreaks in Utah and Pennsylvania, according to U.S. government tracking, including 1.4 million laying hens in Cache County, Utah, on April 25.

So far this year, 33.38 million domestic flock birds have been killed in 29 states to halt the spread of the virus. No outbreaks have been reported in domestic flocks in Tennessee, but the virus has been found in wild birds here.

The last time avian flu was an issue in the United States was 2015.

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“This particular variant is better adapted to wild birds than the one we had in 2015,” said Richard Webby, a world expert in avian influenza at St. Jude Children’s Research Hospital. “That one came and went relatively quickly. I have some concerns that this particular virus may not do the same.”

This virus is genetically different from the variant that besieged the poultry industry in 2015-2016. Because wild birds are more susceptible, there is potential they will continue re-infecting domestic flocks through droppings, which then get tracked into yards and large-capacity chicken production areas.

“We have never had this potential situation where these highly pathogenic forms of avian flu could potentially become endemic,” Webby said. “We get outbreaks from time to time. You depopulate the affected flock; it’s relatively easy to clear up.

“But if it’s in wild birds, eradication becomes almost impossible,” he said. “That changes the environment for the poultry sector in the United States.”

He expects the U.S. government may have to mandate that chickens and turkeys be vaccinated.

The human health risk is low, although there are cases where variants of the virus have affected people in China and England. Experts say more cases in birds heightens the chance the virus will mutate and jump into humans.

Birds affected by the virus have cold symptoms, including puffy eyes and nasal secretions. The virus is spread through secretions and manure.

“A respiratory infection looks the same in all species,” says Tom Taylor, University of Tennessee Extension poultry expert. “If folks know what they are looking for, puffy eyes coughing and sneezing, they’ll recognize it.

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“If they have never seen it before or haven’t had chickens before, it can take off,” Taylor said. “There are a lot of people since the pandemic started that got chickens. These folks may not know what to look for.

“In all the breaks we are finding around the country, more than likely someone probably tracked some wild bird manure into a facility in a backyard or in a commercial chicken house,” he said. “We can’t control where ducks and geese are going to fly. If a flock of wild birds fly over your farm and leave droppings, that’s a risk.”

Because backyard chicken operators do not have to register their flocks, cases of avian flu may be undercounted. People eating eggs or meat from backyard producers should take extra precautions to cook them thoroughly.

Proper handling and heating food to 165 degrees kills bacteria and viruses, including the viruses that cause avian flu, said Janie Burney, Extension nutrition specialist and professor at University of Tennessee-Knoxville.

“USDA and Centers for Disease Control are following aviary influenza closely because individuals who work in production or hunt could be at greater risk,” Burney said. “Also, because flu viruses are constantly changing, CDC will continue to monitor these viruses to look for genetic or epidemiologic changes suggesting they might spread more easily to and between people and cause serious illness.”

Weeby expects the U.S. poultry industry could be on the precipice of long-term infections.

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“By last count, 20% of the layer populations in Iowa has been depopulated,” he said. “That is the largest egg-producing state in the U.S. That will have an impact on supply.

“If it’s just circulating in poultry, it is comparatively easy to try to eradicate,” Weeby said. “But when it is in something that is free, flying north, south, east and west, then it becomes a whole different story.”

The Harmons bought their chickens 10 months ago. They are watching them every day, including a “broody” hen, belligerent because she is trying to hatch an unfertilized egg.

“We don’t have roosters, so that is not going to happen,” said Alex Harmon. “We’re watching to see that she is just broody and that there is not something wrong with her.”

But birds do fly through their yard, particularly in the front where they are building a large garden.

“Aside from intense bird netting, I don’t know what we can do to put a stop to that,” said Terrell Harmon.

The family is enlarging its coop in case its free-ranging birds have to be confined.

Meanwhile, Taylor’s phone has not stopped ringing since March and the first reports of the government having to kill large numbers of chickens.

“People want to know what they can do,” he said. “There’s not a cure. The best thing you can do is prevent it from happening, and a lot of that is just common sense.”

For instance, if you keep chickens and have to go to the feed store or poultry supply house, where lots of people who keep chickens will also be going, don’t check your chicken house or backyard pens in the same clothes you wore to the store, he said.

“Use boots you can wear only at the facility. We can’t overemphasize biosecurity enough. It’s a huge part of keeping everything safe until the weather warms up and the migration season is behind us.”