Bird Flu: How It Can Spread To Humans

I’ve been following the news about the recent cases of bird flu in farmers who work with cows, and it’s worrisome. Do we know how the bird flu is spreading to people? Can we get it from eating meat or drinking milk?

Sincerely,
"Friend of a Farmer"

It’s a situation that’s worrisome to infectious diseases experts, too. Bird flu has been around for a long time and it’s very prevalent in wild birds as well as poultry raised on farms. While we’ve known for a while that it can spread quickly among birds, we haven’t really seen it spread to humans until recent years.

The big change has occurred in the past two years, where we’re seeing strains of avian influenza jumping from birds into mammals, and then the mammals are quickly spreading it amongst themselves. We’ve seen this happen in goats, seals, foxes, and now it’s happening in cows.

So far, the cases of avian influenza (H5N1) that have occurred in humans have all involved people in close contact with infected birds or mammals. We aren’t seeing any cases of avian flu that were spread from one person to another.

The main method of transmission with influenza is airborne, so the theory is that these farm workers were exposed to the virus through inhaling droplets that contain the virus. They might also have touched something contaminated with the virus and then touched their eyes, nose, or mouth.

However, there might be additional mechanisms of spread with this virus. For instance, we know that unpasteurized milk has been shown to contain the virus, so if someone is drinking raw milk, they could be getting exposed that way. Consuming raw meat from an infected animal is another possible method of transmission.

The Centers for Disease Control and Prevention (CDC) says the risk to members of the general public who don’t have exposure to infected animals remains low. But one big concern right now is that if a farm worker is exposed to avian flu and then gets exposed to the seasonal flu at the same time, then a "genetic mix-up" might occur that would enable the mutated virus to more easily spread from one human to another. So that’s why public health officials have been advocating for more protection for farm workers.

According to the CDC, people with close or prolonged, unprotected exposures to infected birds or other animals (including livestock), or to environments contaminated by infected birds or other infected animals, are at greater risk of infection and should take the following precautions:

• Wear recommended personal protective equipment when interacting with infected or potentially infected animals.
• Monitor their health for 10 days after their most recent exposure.
• Avoid close, long, or unprotected exposures to sick or dead animals, including wild birds, poultry, other domesticated birds, and other wild or domesticated animals (including cows).
• Prevent unprotected exposures to animal poop, bedding (litter), unpasteurized ("raw") milk, or materials that have been touched by, or close to, birds or other animals with suspected or confirmed A(H5N1) virus.

• Find out how rapid flu tests work.
• What are the side effects of Tamiflu?
• Learn more about Northwell’s infectious disease practice.