The avian flu virus infecting dairy cattle herds, poultry, and many wild birds in the United States is an emerging situation with unanswered questions. At this point, no case of a human passing the virus along to another human has been identified. This means that it’s unlikely to become widespread among humans in its current form, and the threat to human health is still low, at least for now.
Just like last spring, migratory wild birds have brought avian flu (also called bird flu, H1N5, highly pathogenic avian influenza, or HPAI) to the US. The latest news is that cows in several U.S. dairy herds have become infected. Earlier this week, the CDC announced that some barn cats and a raccoon have tested positive avian flu. Globally, lots and lots of other species have been infected. These are troubling developments because they hint that the virus may be adapting to infect mammals more easily.
The good news is that so far, this flu virus has not evolved the ability to easily bind to human cells and cause human-to-human transmission. A few humans have become infected, but the circumstances of these infections are not something you’d encounter every day. The human infections so far have all been the result of exposure to very high amounts of virus in aerosolized particles, like during slaughter or processing. And the humans who got infected did not pass the virus along to other humans.
The United States CDC, the USDA, the FDA, and other health and safety organizations are all over this. You can see the latest US surveillance info at USDA. That said, this author is among those who have some questions about how systematic that surveillance is, and whether it could be improved. A recent NYT piece revealed that the USDA is not systematically testing cattle. They are testing only symptomatic cattle and only a handful of them. And, they aren’t testing pigs at all. This is troubling because pigs are really good at getting influenza viruses.
It’s also troubling to me because it’s yet another reminder of how important systematic testing is, and the fact that in the United States we just don’t do it. Frankly, it gives me flashbacks to the early days of COVID-19 when we had absolutely no idea how widespread community transmission was.
It’s not clear how dairy cattle are being infected. Experts at the USDA say that it is not spreading like a respiratory virus among cattle. That’s weird, because usually influenza viruses spread through respiratory droplets. The USDA reports that they think cows may be getting infected through their feed supply or through the milking process, but this answer only raises more questions.
High amounts of influenza virus have been found in milk from infected cows, and non-infectious fragments of virus have been found in pasteurized milk.
If you’re worried about the milk: pasteurization eliminates any risk from consuming the milk of infected cows, so drinking standard grocery store milk does not pose a threat to health. Raw milk drinkers, beware. Other FAQs about avian flu in dairy cows are available from USDA here.
This avian flu is very widespread among wild birds. Six million birds are estimated to have been infected this year. The birds most likely to be infected are waterbirds (ducks, geese, and swans). Most common songbirds or other birds found in the yard, like cardinals, robins, sparrows, blue jays, crows, or pigeons, do not usually carry bird flu viruses that are dangerous to poultry or people. Bird flu viruses can easily spread from wild birds to poultry, like chickens and turkeys. Some wild birds can carry bird flu viruses without appearing sick, but it very often kills chickens and turkeys. Infected cows often have symptoms but usually make a full recovery.
What if the virus makes the species jump and starts causing human-to-human transition? Well… that’s the classic pandemic scenario. But don’t panic, we have some advantages here. For one thing, there is an existing, approved human vaccine for avian influenza, but it’s not available to consumers because it isn’t needed at this time. Antiviral medications for flu (such as Tamiflu) are also effective and widely available. And, your past years’ seasonal influenza vaccination would likely offer some protection against a new strain of influenza, though incomplete.
All of this said, this is an uncertain situation. My Magic 8-Ball says: “Cannot predict now.” We’ll just have to see what happens next.
What to do to protect yourself and others:
- Avoid contact with wild waterfowl.
- Do not handle sick or dead wild birds and other animals. If you must handle them, wear a good respirator mask and clean your hands, clothes, and shoes afterward.
- Report sick or dead birds to the USDA: 866-536-7593.
- Keep your pets away from sick or dead birds and other animals.
- Don’t consume raw milk, or at least avoid aerosolizing it (using a blender, for example).
- Get your annual flu vaccine. See our post from last year for more about why this is helpful.
If you raise backyard chickens, ducks, or other poultry: your birds can easily get avian flu if they have contact with infected wild birds or share food, sources of water, and environments with them. You should review your biosecurity practices. Separate your birds from wild birds by penning them in. Keep a separate set of clothes and shoes for use while in the coop. Wash hands before and after flock chores. Don’t share equipment between flocks.
If you work closely with livestock animals day-to-day, there are a lot of special considerations that you need to be aware of. Keep on top of this situation and the recommendations of CDC and the USDA as well as your State’s departments of health and agriculture.
