People get bird flu primarily through direct or close contact with infected birds, poultry, or other animals, including dairy cattle. The virus enters your body through your eyes, nose, or mouth, either by inhaling contaminated droplets or by touching a contaminated surface and then touching your face. Since February 2024, 71 human cases of H5 bird flu have been reported in the United States, with 41 of those linked to exposure at dairy cattle operations.
Direct Contact With Infected Animals
The most common route of infection is spending time near sick or dead birds, poultry, or infected livestock. These animals shed the virus in their saliva, nasal secretions, and droppings. When you handle an infected bird, work near a flock, or milk an infected cow, you can breathe in tiny droplets containing live virus or get splashed with contaminated fluids. Even brief exposure at a live poultry market has been enough to infect people in past outbreaks.
Activities that generate a lot of airborne material carry the highest risk. Culling infected poultry flocks, defeathering birds, and milking dairy cows with active infections all expose workers to large amounts of virus at once. The more virus you encounter, the greater the chance of infection.
Indirect Contact Through Contaminated Surfaces
You don’t have to touch an infected animal directly. The virus survives on surfaces and in the environment long enough for indirect transmission to occur. Bird droppings, contaminated litter, soiled egg collection containers, and raw milk can all carry live virus. If you touch any of these and then rub your eyes, nose, or mouth, the virus can establish an infection.
How long the virus lasts on surfaces depends on the material and temperature. At room temperature (around 72°F), H5N1 survives with a half-life of roughly 2.5 to 3.3 hours on common materials like plastic, stainless steel, and rubber. That means it can remain infectious on equipment or countertops for several days before fully breaking down. In cold environments, like a refrigerated barn or winter conditions, the virus persists much longer, with half-lives stretching to over a day on plastic and steel surfaces. In wastewater at room temperature, the half-life is about half a day, and full inactivation can take more than two weeks.
Raw Milk and Food Safety
One transmission pathway that has drawn attention during the current dairy cattle outbreak is raw (unpasteurized) milk. If milk from an infected cow splashes into your eyes or you touch contaminated milk and then touch your face, infection is possible. Whether drinking raw milk from an infected cow can cause infection is still not fully established, but the CDC notes it’s plausible and advises against it.
Pasteurization kills the virus in milk. Cooking poultry, eggs, and beef to the proper internal temperature (165°F for poultry and eggs) also destroys it. A small number of human infections in Southeast Asia have been linked to consuming raw or undercooked poultry products, including blood dishes, though no such cases have been confirmed in the United States from properly handled and cooked food.
Who Is Most at Risk
Bird flu infections in humans remain rare and are concentrated among people with occupational exposure to animals. The workers most at risk include:
- Poultry farm workers at broiler, layer, and turkey operations, as well as hatcheries and processing plants
- Dairy farm workers who milk or handle infected cattle
- Disease control workers involved in culling operations
- Live bird market workers
- Wildlife biologists who capture or handle wild birds
- Animal rescue and control workers who encounter infected animals
The general public’s risk remains low. Most people simply don’t have the kind of prolonged, close animal contact that leads to infection.
How the Virus Gets Into Your Body
Bird flu viruses need to reach the moist tissue lining your eyes, nose, or throat to start an infection. This happens in three ways: inhaling airborne droplets or dust particles carrying the virus, getting a direct splash of contaminated fluid into your eyes or mouth, or transferring the virus from your hands (or gloves) to your face. Your eyes are a particularly vulnerable entry point. In many recent U.S. cases, redness and irritation of the eyes was the earliest and sometimes only symptom.
Once the virus enters, symptoms typically appear within about three days, though the range spans two to seven days. Eye symptoms like redness and irritation can show up even faster, within one to two days of exposure.
How Workers Protect Themselves
For people who can’t avoid contact with potentially infected animals, the key is creating barriers between the virus and your eyes, nose, and mouth. In high-exposure settings like depopulation operations, workers wear a full kit: a fitted particulate respirator, sealed safety goggles, fluid-resistant coveralls, boot covers, head covers, and disposable gloves. A face shield may go over the top of goggles and respirator to block large splashes, though it’s not a substitute for goggles on its own.
Each layer serves a specific purpose. The respirator blocks small droplets and also physically prevents you from touching your nose and mouth while working. Goggles keep droplets and splashes out of your eyes and stop the unconscious habit of rubbing them. Outer garments, from coveralls to boot covers, keep contaminated material off your skin, hair, and clothing so you don’t accidentally transfer it to your face later when you’re taking everything off.
Person-to-Person Spread
Bird flu does not currently spread easily between people. The virus is adapted to bind to receptors deep in bird and animal respiratory tracts, not the upper airways of humans. Rare instances of possible limited person-to-person transmission have been documented globally, typically between household members caring for a very sick relative, but sustained spread has not occurred. This is the primary reason bird flu remains an occupational hazard rather than a community-wide threat. If the virus were to mutate in ways that allowed efficient human-to-human transmission, the risk picture would change substantially.