How do you get infected with bird flu?

How do you get infected with bird flu?



CNN

As bird flu infections increase in dairy cows and chickens, cases in humans are also increasing, leaving many people wondering whether they may be at risk from this recently arrived virus.

Bird flu infections are rare in humans. According to the U.S. Centers for Disease Control and Prevention, 61 human cases have been confirmed in the U.S. this year, and all but three involved people working on poultry or dairy farms.

As the name suggests, bird flu viruses prefer to infect birds. They enter cells by attaching themselves to sugars that protrude from the surface of the cells called sialic acids. H5N1, the avian flu virus behind the ongoing U.S. outbreak, has actually only shown an affinity for the types of sialic acid receptors most commonly found in the respiratory tract of birds.

But flu viruses can also mutate quickly, and since 2022 H5N1 has been infecting a growing variety of mammals, including dairy cattle.

This puts scientists on alert because the more it circulates in animals, the more successful it is at finding new hosts.

A study published last week in the journal Science showed that only a key change in the virus’s genetic material would allow it to bind to the types of sialic acids most commonly found in people’s noses and lungs. But it’s almost impossible to predict when that might happen – or if it ever will.

When people become infected with bird flu, it almost always happens through contact with infected animals. All but one of these so-called spillover infections were mild.

The first serious case in the United States was announced this week in a person in Louisiana who remains hospitalized in critical condition. The CDC said Wednesday that the person was exposed to sick and dead birds on his property, not commercial poultry.

No one infected with H5N1 in the United States is known to have transmitted the infection to anyone else. For this reason, the CDC considers the current risk to the public to be low, but there are certain occupations and situations that may increase a person’s risk of contracting bird flu.

The two groups most at risk are farm workers who work with cows or poultry and people who keep backyard herds, Dr. Michael Osterholm, who directs the Center for Infectious Disease Research and Policy at the University of Minnesota.

Birds shed the virus through their saliva, mucus and feces, and it can become airborne when their droppings and feathers are disturbed in stables, particularly during culling operations.

“It could be in the air,” Osterholm said. “So it’s not just about touching the birds, it’s just the dander and all the dust that comes from handling birds.”

The virus also affects the udders of dairy cows, and studies have found high levels of the bird flu virus in raw or unpasteurized milk.

Dairies’ milking parlors are humid environments, and workers can become infected if they get a splash of raw milk in their eyes or if they get milk on their hands and then rub their eyes. Droplets of virus-laden milk can also become airborne when sprayed from milking equipment.

One of the most noticeable symptoms in infected farm workers was red, irritated eyes or conjunctivitis. This may be because the human eye has the same types of sialic acid receptors that are most common in birds.

How about raw milk?

Cats became infected after drinking raw cow’s milk. There have also been reports of calves becoming sick after drinking infected milk.

“We don’t have the same data for people,” Osterholm said.

No human infections have been linked to raw milk consumption, although a toddler in California recently tested positive for flu after drinking a large amount of raw milk. The CDC has not been able to confirm whether the infection is present However, since it was bird flu, this child is listed as a suspected case.

But there are plenty of them Data on other pathogens that can occur in raw milk, even without specific evidence of H5N1. In 2023 and 2024, outbreaks of E. coli and salmonella infections were traced to raw milk. It can also harbor other pathogens such as Listeria and Campylobacter.

Pasteurization kills all of these harmful germs, including H5N1, a recent government study shows.

However, this is not the case with cooling. A recent Stanford University study that spiked raw milk with flu viruses and tested it on cells in a Petri dish found that the virus can continue to infect cells for up to five days after refrigeration.

The best way to protect yourself from bird flu is to avoid sources of exposure, according to the CDC.

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People can become infected with bird flu if enough of the virus gets into their eyes, nose or mouth, or if they inhale it. This usually requires close and prolonged contact with infected animals.

For this reason, the CDC recommends that people stay away from sick or dead birds or other animals and avoid touching surfaces contaminated with feces or saliva, such as bedding or bedding.

If you must handle sick birds, cows or other animals, such as on a farm or at a rescue center, the CDC recommends wearing appropriate personal protective equipment, or PPE. This includes:

  • Glasses
  • Disposable gloves
  • An N95 face mask
  • Overalls
  • Rubber boots

Since raw milk can contain so many dangerous germs, experts recommend avoiding it and opting instead for pasteurized milk products.

But what about raw eggs? According to the U.S. Food and Drug Administration, eggs from an infected flock are unlikely to reach store shelves because birds quickly become ill with avian flu and there are safeguards, such as inspections, in place to prevent contaminated eggs from reaching the market.

It’s still a good idea to cook eggs and poultry to a safe temperature and prevent cross-contamination between raw and cooked foods in the kitchen.

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