Bird flu jumped to cows, then to a human. Should we be worried? (2024)

Bird flu is, famously, a disease that infects birds. But earlier this week, federal and state authorities reported that a person in Texas had tested positive for the disease, the second person in the US to contract avian influenza in the last two years. Stranger still, the patient didn’t contract the disease from a sick chicken or wild bird but from a cow, which was presumably infected with the virus. Rarely, if ever, have mammals infected humans with bird flu.

The Texas patient reported only one mild symptom — namely, pink eye — and is recovering, according to the Centers for Disease Control and Prevention. Yet the news is the latest in a long string of recent headlines that raise concerns about the risk that bird flu poses to public health.

In the last few years, avian influenza has ravaged domestic flocks, causing farmers to cull chickens by the millions. This week, the virus was detected at a facility run by the largest chicken egg manufacturer in the US and was confirmed in dairy cows in a fifth US state. It has also been decimating wild birds and many marine mammals including seals and sea lions. And the virus continues to spread, so far reaching penguins in Antarctica and at least one polar bear in the Arctic.

These developments are concerning. But how worried should we be? Here’s what to know about the risk to humans and to the millions of farmed and wild animals.

Bird flu basics: What it is, and where it comes from

Avian influenza, or bird flu, is a general term for the disease caused by influenza viruses that primarily infect and spread among poultry and some wild birds. They’re distinct from viruses that cause the flu in humans, though they’re related.

These avian viruses are quite common. They’ve been circulating for eons among wild waterfowl, such as ducks and geese, without causing them much harm. Mild forms of infection are called “low-pathogenic avian influenza,” or LPAI, which means they’re typically not deadly to wildlife.

The type of avian influenza spreading today is different.

Occasionally, an LPAI virus can jump from wild birds to birds on poultry farms. As the virus replicates in densely packed warehouses of farmed birds, it can quickly evolve and adapt in ways that make it highly deadly to poultry. At that point, it gets dubbed a “highly pathogenic avian influenza virus,” or HPAI virus. That’s what’s circulating today — an HPAI virus.

Highly pathogenic bird flu has caused outbreaks on poultry farms many times in the past that have killed thousands to millions of farm birds. What makes this particular form of avian influenza virus so unusual is that it easily spreads and causes severe disease among wild birds and an increasing number of mammals. That’s rare.

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The current strain of avian influenza spreading today descended from a virus that caused an outbreak on a goose farm in Guangdong, China, in 1996. The US first experienced one of these goose farm virus outbreaks in 2014 and 2015, which caused the death and culling of tens of millions of poultry birds and an unknown number of wild birds. Then in 2021, a related version of the virus arrived in the US — the cause of the current outbreak — that appears much better equipped at infecting wild animals.

Bird flu became big news in the months that followed, in 2022, when it started spreading through poultry farms. Farmers were forced to cull tens of millions of turkeys and egg-laying hens, often using a gruesome approach. It cost the federal government and the poultry industry hundreds of millions of dollars to manage and sent egg prices soaring in late 2022 and early this year. Just this week, Cal-Maine Foods, the country’s biggest fresh egg producer, reported that it had to kill 1.6 million hens — more than 3 percent of the company’s entire flock — following an outbreak in Texas.

Another person got sick. Does that up my risk?

Since 2022, the outbreaks of bird flu on poultry farms have been mostly sporadic, with flareups here and there. But the virus continues to spread to different places and to different kinds of animals, including both wild and domestic mammals.

Early in 2023, the virus killed thousands of sea lions. This spring, meanwhile, officials found bird flu in Minnesota goats and in herds of dairy cows in Texas, Kansas, Michigan, Idaho, and New Mexico. (The agency says milk, which must be pasteurized before entering the commercial food supply, remains safe to consume.)

“Although we don’t yet completely understand the factors that led to infection of the dairy cows with HPAI, it is possible that unique viral properties combined with epidemiological and environmental conditions all played a role for the spillover of HPAI into cattle,” said Diego Diel, an associate professor at Cornell University’s college of veterinary medicine.

What makes this concerning is the obvious fact that humans are mammals, too. As the virus makes the jump from birds to mammals, what’s stopping it from jumping to all of us?

In the last few years, a couple dozen people worldwide — mostly in parts of Asia — have tested positive for this particular kind of bird flu, all of which likely came into close contact with infected animals. Symptoms may be nonexistent or subtle, such as eye redness or a mild flu, or they may show up as a fever (above 100 degrees Fahrenheit) and pneumonia and can prove fatal. In the last two decades, more than 800 people have been infected with bird flu globally, and more than half of them died.

In the US, however, human infections — let alone deaths — are rare.

The first human case of avian influenza from the current outbreak was in 2022, when a Colorado farmer who was involved in killing chickens tested positive. The man said he was tired for a few days but quickly recovered.

The person in Texas, meanwhile, tested positive earlier this year, after he was exposed to dairy cattle that were “presumed to be infected” with highly pathogenic bird flu, per the CDC. The patient is taking an antiviral medication and recovering, the agency said.

As for the rest of us?

First, the good news: The bird flu that infected the person in Texas (who is a dairy worker, per Politico) is almost certainly incapable of spreading dangerous infections to other people around the planet, experts say. Simply put, the virus currently does not have the proper biological machinery to easily invade — let alone circulate among — humans. We have very different physiologies than birds and other animals that HPAI easily infects. These workers got sick because they were likely exposed to very high levels of virus. (If you want to go deeper, check out our earlier explainer on this.)

TL;DR: The chances of you getting bird flu anytime soon are extremely slim.

The bad news is that influenza viruses evolve quickly, and unpredictably. Not only do they mutate, but they can also swap entire portions of their genomes with other viruses, creating new Franken-viruses, if two or more of them infect the same host. Under the right circumstances, this evolution could give the virus the tools to replicate more easily in mammals, which could make future strains of bird flu more threatening to humans.

Scientists are now racing to figure out what, exactly, those conditions might be. More specifically, they’re looking for signs that the virus is picking up adaptations that make it more likely to replicate within mammalian cells and — critically — to spread from mammal to mammal, such as cow to cow or seal to seal. “There are many unanswered questions about the current HPAI outbreak in cattle, but one of the key questions is whether the virus is being transmitted from cow to cow,” Diel said.

One new study suggests that the virus has adapted to marine mammals and may be able to spread among them. USDA officials, meanwhile, have said that transmission of avian influenza among cattle “cannot be ruled out,” in a recent update about the dairy cow outbreaks. “This virus is still relatively low risk for humans,” Marcela Uhart, a wildlife veterinarian with the University of California Davis School of Veterinary Medicine and senior author of the new study, said in a February statement. But she also had words of caution: “As long as the virus continues to replicate in mammals, it may make it a higher concern for humans. That’s why it’s so important to conduct surveillance and provide early warning.”

How should we be thinking about bird flu?

Obviously it’s not great that another human tested positive for bird flu. Again, he will likely be fine.

But this story is not yet over. Scientists are still trying to figure out how the virus is changing and what it means that cows are getting sick. The virus could evolve to become a risk — especially to farm workers and people who work with wild animals — underscoring the importance of monitoring the outbreak closely.

There’s another tough reality here: Industrial animal agriculture, with thousands of animals packed together in warehouses, is a breeding ground for bird flu. So even if this current outbreak among birds wanes, we’ll likely continue to see new outbreaks in the decades to come, across different species. Eventually, that could pose a more serious risk to humans; the more chances bird flu gets to evolve, the more opportunities it has to turn into something dangerous.

That raises complex questions about our food system, and how we can make it healthier for humans — not to mention farmed animals and wildlife. To prevent or slow the spread of zoonotic diseases, like bird flu and Covid-19, governments, food companies, and farmers will need to invest heavily in surveillance (including of wild birds) and even vaccines, and they may ultimately need to make much more serious changes to animal agriculture.

Update, April 3, 2:33 pm ET: This story was originally published on April 2 and has been updated with new detections of bird flu in dairy cows and egg-laying hens.

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Bird flu jumped to cows, then to a human. Should we be worried? (1)

Bird flu jumped to cows, then to a human. Should we be worried? (2024)

FAQs

Bird flu jumped to cows, then to a human. Should we be worried? ›

A farm worker in Texas contracted the virus amid an outbreak in dairy cattle. This is the second human case in the US; a poultry worker tested positive in Colorado in 2022. The virus strain identified in the Texan farm worker is not readily transmissible between humans and therefore not a pandemic threat.

What happens if a human gets the bird flu? ›

Bird flu is a respiratory virus. In severe cases in humans, it can cause pneumonia, according to the CDC. Symptoms can include fever, cough, sore throat, runny nose, body aches, headaches, fatigue and shortness of breath or difficulty breathing.

Can cows catch bird flu? ›

A virus that has killed hundreds of millions of birds has now infected cattle in six US states, but the threat to humans is currently low. Researchers are closely monitoring the spread of a worrisome strain of avian influenza to cattle — and one person — at farms in six US states.

Should we be worried about bird flu? ›

Should people worry about bird flu affecting them, or their eggs or milk? The CDC said the overall risk posed by the bird flu to public health remains low. The average consumer shouldn't be too concerned, as long as they heat their food properly and drink pasteurized milk, experts said.

What is the mortality rate for the bird flu in humans? ›

From 1 January 2003 to 26 February 2024, a total of 254 cases of human infection with avian influenza A(H5N1) virus have been reported from four countries within the Western Pacific Region (Table 1). Of these cases, 141 were fatal, resulting in a case fatality rate (CFR) of 56%.

How do you treat bird flu in humans? ›

In general, treatment with the antiviral medicine oseltamivir (Tamiflu) or zanamivir (Relenza) may make the disease less severe. For the medicine to work, you need to start taking it within 48 hours after your symptoms start.

Is there a vaccine for bird flu for humans? ›

There are no specific vaccines for preventing influenza A(H5N1) virus infection in humans. Candidate vaccines to prevent H5 infection in humans have been developed for pandemic preparedness purposes.

Can humans get sick from eating birds with bird flu? ›

No. Humans cannot become infected by eating fully cooked poultry or eggs. However, according to the CDC, “uncooked poultry and poultry products (like blood) could have been the source of a small number of bird flu virus infections in people in Southeast Asia.”

Can you get bird flu from holding a bird? ›

Because human infections with these bird flu viruses are possible, all people with direct or close exposure to infected well-appearing, sick, or dead birds, infected flocks or contaminated surfaces should be monitored for illness for 10 days after their last exposure.

Why can't you eat birds with bird flu? ›

Avian flu is not a foodborne illness, which means you cannot contract it from eating poultry that has been cooked properly.

Can you survive bird flu? ›

Bird flu, also known as avian influenza, is a type A influenza virus. It is lethal to poultry and is potentially fatal in humans. Bird flu spreads between both wild and domesticated birds. It has also been passed from birds to humans who are in close contact with poultry or other birds.

Can you be immune to bird flu? ›

Humans also do not have natural immunity to avian flu.

Is bird flu high risk? ›

But federal officials and scientists stress the risk to the public still remains low. So far, the virus does not appear to have mutated in a way that would make it significantly more dangerous.

How many cases of bird flu in humans have there been? ›

No case of severe illness or death with HPAI A(H5N1) virus infection has been reported in the United States. Since 1997, more than 900 sporadic human cases of HPAI A(H5N1) have been reported in 23 countries, with more than half of these cases resulting in death.

How long does bird flu last? ›

The average incubation period of bird flu H5N1 is two to five days, though it can last up to 17 days. (3) For H7N9, the average incubation period is five days, and can last up to 10 days. (3) Both viruses have a longer incubation time than that of seasonal influenza.

Can dogs get bird flu? ›

Bird flu (avian influenza) viruses can infect mammals, including cats, dogs, ferrets and other pets. Contact your vet if you have concerns about the health and welfare of your pet.

Can humans get bird flu from eating chicken? ›

Avian flu is not a foodborne illness, which means you cannot contract it from eating poultry that has been cooked properly. And in the event a flock does test positive, it will not enter the food chain. But as always, you should follow proper handling and cooking when preparing raw chicken.

Can a human make a bird sick? ›

Humans do not transfer cold or flu viruses to their birds. In fact, there a only a couple of uncommon viruses that can be passed along to them, but it is very difficult to do so. We spend much more time in and around their body fluids than they do ours.

How do you get bird flu virus? ›

The influenza virus, called H5N1, is highly pathogenic, meaning it has the ability to cause severe disease and death. But while its spread among cows was unexpected, people can catch the virus only from close contact with infected animals, not from one another, federal officials said.

Can birds cause respiratory problems in humans? ›

Chlamydia psittaci is a type of bacteria that often infects birds. Less commonly, these bacteria can infect people and cause a disease called psittacosis. Psittacosis can cause mild illness or pneumonia (lung infection). To help prevent this illness, follow good precautions when handling and cleaning birds and cages.

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