A Beginner’s Background on Bird Flu, or Highly Pathogenic Avian Influenza (HPAI)
Full transparency: I do not specialize in livestock, dairy, or pathology. I do not spend much of any part of my day thinking about these topics. But the headlines about “bird flu” are getting hard to ignore, and I’ve been asked about it by non-agriculture friends.
I can’t provide hot takes, but I can provide some background and helpful resources that I uncovered while trying to learn more.
TL;DR
Avian influenza is once again striking laying hens across the US, causing price increases in eggs.
This Spring, avian flu crossed from birds to dairy cattle for the first time.
Transmission then crossed species again, from cattle to human, in one case in the US this spring.
Federal agencies insist that risk to humans is incredibly low, but reported human cases among farm workers may be under-reported. Avian influenza has caused public health concerns for humans worldwide in the past, but not yet at pandemic levels. This is certainly a concern.
The federal government is investing some (and only some) resources to increase testing and monitoring, but is facing resistance at state and local levels.
I had a lot more questions, so keep reading for more background.
What’s up with this bird flu?
“Bird flu” is an informal name given to avian influenza, and the strains we’re worried about here are Highly Pathogenic Avian Influenza, or HPAI.
The most recent concerns about HPAI were set off in Europe and Asia in 2020, according to the US Fish and Wildlife Service, and CBS cites the first detection of the strain in the United States occurring in Michigan in 2022. The disease can cause a loss of productivity, illness, and death amongst affected poultry, leading poultry companies to cull millions of birds in an effort to stop the spread.
This loss of productivity is cited as a leading cause of increased egg costs from 2022 to today, above and beyond what would be expected from post-COVID inflation. The USDA reported price stabilization between 2022 and 2023, but notes that prices are again rising for eggs and poultry as a result of HPAI impacts.
The current strain of concern is referred to as HPAI A(H5N1). This translates to:
HPAI = Highly Pathogenic Avian Influenza
A = Type A
A (H5N1) = the type of virus responsible for this strain of avian influenza; A (H5) and A (H7) viruses are specifically responsible for the HPAI that is highly contagious in poultry. A (H5N1) is one of the most common types of avian flu that can spread to humans, according to the Cleveland Clinic, but actual infection in humans is rare.
The headlines feel scary.
Avian influenza passes between wild and domestic birds (from “free-flying waterfowl” to chickens and turkeys), hence the “avian” influenza moniker. But A(H5N1) can spread from birds to other kinds of animals, including mammals like cats and cows that humans interact with (see the Cooperative Extension graphic, below). Transmission to humans (when the virus “jumps the species barrier”) has caused severe disease outside of the United States, but less than 1,000 cases have actually been reported worldwide since 1997 and only two ever in the United States.
One case of A(H5N1) was reported in the US in early April; they most likely contracted the illness from an infected dairy cow in Texas. The CDC stated that the patient suffered conjunctivitis (pink eye) as their only symptom. A previous case of A(H5N1) in a human occurred in Colorado in 2022. The CDC and FDA say that risk to humans remains extremely low.
This singular human contraction caused big news, as did reports in March (2024) of A(H5) in dairy cows in Texas and Arkansas (this A(H5) being the same “genetic clade” that is widespread among birds). The virus has been confirmed in dairy cattle in 9 states, and in 48 states in chickens.
The concern I’m reading about in headlines is less about the risk of contracting avian flu from interacting with farm animals (something few of us do regularly) and more about contracting avian flu from eating infected eggs or drinking infected milk.
What is the government doing about it?
Depends on the level of government, and don’t forget about industry.
The USDA, FDA, and CDC all have murky jurisdiction over this issue. That jurisdictional quagmire is a subject for another day. To keep it short: the FDA oversees milk and whole egg production, and the USDA oversees meat, poultry, and eggs outside the shell. Because of the concerns around milk and whole eggs, the FDA is leading most federal communications that I’ve found. The CDC is responsible for identifying and containing disease outbreaks.
The departments are putting out an aligned front with similar messaging.
Eggs are safe - so long as they are prepared properly (putting the responsibility on the consumer, not the producer or processor). This means cooking whole eggs until whites and yolks are hard, because whole eggs are not pasteurized on the inside (egg products, like egg whites, are pasteurized).
Chicken is safe - so long as it is prepared properly (again, putting the responsibility on the consumer)
Milk is safe - so long as it is pasteurized (avian flu has been detected in raw/unpasteurized milk, according to the USDA and WHO)
The FDA is making $8 million available to support their monitoring of the commercial milk supply (that is… not a lot of money)
The FDA released this statement:
“The U.S. Department of Agriculture (USDA), the U.S. Food and Drug Administration (FDA), and the Centers for Disease Control and Prevention (CDC), along with state partners, continue to investigate an outbreak of highly pathogenic avian influenza (HPAI) virus impacting dairy cows in multiple states.”
As I write in the next section, this partnership betwen federal and state departments may be more tenuous than the FDA suggests.
This “partnership” largely involves inspections, testing, and monitoring for now. As mentioned above, producers have also killed millions of birds in an effort to contain the virus. While the virus can rapidly kill birds, the American Veterinary Medical Association suggests that cattle have a much higher tolerance to the illness, predicting little to no mortality.
Some questions may be fair to ask.
Limited federal oversight. The USDA is notoriously limited in what they can do when inspecting meat, poultry, and egg processing facilities, as has been raised in documentaries like Poisoned recently released on Netflix.
Limited cooperation from farmers and states. Politico reports that state departments of agriculture in both red and blue states are pushing back on federal monitoring and testing attempts. State departments want all testing and intervention to be voluntary, and states like Texas, where the first cases of bird flu in cattle were reported, cite an inability to find any farmers or ranchers willing to participate. Politico’s reporting suggests that more cases of human transmission may have occurred, but not been reported. The USDA announced they will pay dairy farmers to test their herds.
Limited precedent. The safety of milk (and potentially beef) is still an open question because the spread of A(H5N1) to cattle is novel. Available data published by the FDA suggests that pasteurization will work on milk, as it has for egg products (see above). The CDC, FDA, and USDA are partnering to collect and test data on an ongoing basis. The virus has not yet been linked to any cattle raised for meat, only dairy cattle.
What about farm workers?
As Politico reported, it is likely that more farm workers are contracting A(H5N1) than have been reported, but there have been no reported cases of human-to-human transmission. Farm workers may feel pressure from employers not to report symptoms, especially if they have tenuous immigration status. Federal government agencies and Cooperative Extension (see below) recommend the use of PPE when working with potentially infected animals, but compliance and availability of PPE will be left up to individual operations.
Links I found useful:
Regular updates on HPAI from the FDA; this is a good link if you want a one-stop shop
An FAQ from the FDA
Food safety instructions from the USDA
Check out the situation summary prepared for national Cooperative Extension by the CDC, below:
A graphic from the Cleveland Clinic indicating symptoms of bird flu
These symptoms look like regular flu symptoms in humans, so actual cases of bird flu may be under reported. Reporting I found indicates that farm workers working with potentially infected animals like chickens and cows/cattle should be checking for symptoms, but non-farm workers are not currently at risk.
Images from the USDA Flickr.