Bird flu is getting worse — but it’s not yet “cow flu,” experts explain

The bird flu outbreak is growing. On Tuesday, the Centers for Disease Control and Prevention (CDC) reported that 36 dairy cow herds in 9 states have been infected with H5N1, also known as avian or bird flu, as of April 30, 2024. This week, the U.S. Department of Agriculture (USDA) also announced it is collecting samples of ground beef at retail stores in states with bird flu outbreaks in dairy cows. According to NBC News, the agency will test beef to see “whether any viral particles are present.” Previously, viral particles have been discovered in as much as 1 in 5 samples of cow’s milk.

Additionally, the USDA started mandating that dairy cows have to test negative for bird flu before being shipped across state lines. The news comes after several infectious disease experts have criticized the government for not doing enough testing and being “blind” to the true size of the current outbreak — and after a report published in  Emerging Infectious Diseases found that cats died after they were fed raw colostrum from sick cows.

“Our findings suggest cross-species mammal-to-mammal transmission of HPAI H5N1 virus and raise new concerns regarding the potential for virus spread within mammal populations,” the authors wrote. 

Just like humans, birds can get the flu. When that happens, they can pass it on to other poultry — such as chickens, ducks and turkeys. But the most recent strain of avian influenza, H5N1, has jumped species. Instead of only infecting birds, the current outbreak is infecting dairy cows and even spread from a cow to at least one human; which is the first time cow-to-human transmission has happened. The last time a human tested positive for H5N1 was in April 2022 in Colorado when an individual got infected from poultry.

The USDA has said that it is confident that the meat supply is safe and that pasteurized milk is safe to drink.

As Salon previously reported, public health experts are concerned that the more it jumps from animal to animal, or animal to human, the more likely it is to mutate, have human-to-human transmission and get a foothold in the human population. Notably, some strains of H5N1 have a 50 percent mortality rate in humans (fortunately, the one confirmed case from an infected cow was mild.) This is why epidemiologists and infectious disease experts have been publicly criticizing the government’s response and demanding they act fast to contain the spread among animal species.


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“I think we’re slowly inching towards getting some sort of answers for some of our questions,” Katelyn Jetelina, an epidemiologist and author of the newsletter Your Local Epidemiologist, told Salon in a phone interview, in regards to recent developments. “But I am a bit disappointed in the lack of transparency and urgency, particularly with USDA, and it just doesn’t seem that there is an appetite to get ahead in this.”

The USDA has said that it is confident that the meat supply is safe and that pasteurized milk is safe to drink. Notably, Colombia has placed restrictions on beef being transported from U.S. states where dairy herds have tested positive for bird flu.

Jetelina emphasized to Salon that H5N1 isn’t new, and it’s important to communicate that to the public. While some people might be inclined to call it “cow flu,” now that cattle are arguably more prominent than birds in the situation, she said it hasn’t mutated into a novel virus that warrants a name change.

“What we have to see is whether it’s adapted to cattle species, and if it’s circulating only in that species. Then we would call it cow flu.”

“We have to make it very clear that this is not a new virus. It’s not like COVID-19 in October of 2019. It’s existed for over 20 years,” Jetelina said. “And it’s not just among cows, it’s still very much in other livestock as well as wild birds — we’re just paying very close attention to cows right now because this is a new mode of transmission that has really unfolded in the past couple of months.”

Dr. Rajendram Rajnarayanan of the New York Institute of Technology campus in Jonesboro, Ark., told Salon calling H5N1 the “cow flu” is “misleading.” If it is only circulating around cows, then it can be called a “cow flu,” he said. 

“It has not adapted enough,” Rajnarayanan said. “So what we have to see is whether it’s adapted to cattle species, and if it’s circulating only in that species. Then we would call it cow flu.”

Rajnarayanan said it’s also important to emphasize that it’s not a definitive conclusion that the cats from the CDC report died from drinking raw colostrum. It’s possible that the cats got sick from eating infected wild birds, too. Jetelina said the report on the cats emphasizes that raw milk shouldn’t be consumed right now. An estimated 4.4 percent of American adults consume raw milk.

“This is not a virus we want to play around with,” Jetelina said. “It really confirmed that raw milk is just something we don’t want people consuming and we really need to get the public health message out there that that’s never safe, but particularly right now.”

Jetelina said scientists don’t know what happens if someone consumes infected raw milk at the moment, but it’s a good sign that there haven’t been any fatal cases linked to raw milk and H5N1. While experts believe there have been more than one human case from cows, they say it’s a good sign that hospitalizations aren’t rising.

“If it’s going to be a problematic virus circulating, you will see a hospitalization increase,” Rajnarayanan said. “And that, we don’t see.”

Still, more surveillance is needed, he said. 

“It’s not going to become a problem immediately,” he said. “But we have to prevent it from becoming a big deal in the next year.” 

Jetelina agreed. 

“I think one good sign is that even if there are more human cases, they seem to be mild, or asymptomatic, given that they haven’t kind of gone on the radar yet,” Jetelina said. “We just really need to stay ahead of this thing and see how it’s evolving so we can be prepared in case this does jump to humans, for human-to-human transmission.”

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