H5N1 bird flu update: Symptoms, map, human cases, and what to know about the CDC’s response

This week, the Centers for Disease Control and Prevention (CDC) announced that a person had been hospitalized with a “severe case” of bird flu. The hospitalization marks the first time that severe illness has resulted in a person in the United States after contracting the virus. Here’s what you need to know about the bird flu, how far it has spread, and how to protect yourself.

What is H5 bird flu?

The H5 bird flu in question is officially known as the A/H5N1 avian virus. It is a virus that originates and propagates among birds, which can cause influenza in animals infected with it.

However, the virus isn’t limited to birds. It can spread to other animals and to humans.

The H5N1 bird flu isn’t new. The CDC says the virus was first identified in Southern China in domestic waterfowl in 1996. In 1997, it spread to 18 people in China and Hong Kong. Six of those people in Hong Kong died from it. The CDC said that that outbreak would ultimately cause over 860 human infections, and the death rate was more than half of those infected.

Since then, H5N1 has spread across the globe, infecting animals much more than humans. However, the fact that H5N1 can infect humans—and the death rate can be so great—is a reason why health agencies across the world are so keen to monitor any emergence of the disease for fear it could present a grave risk to the public.

What are the symptoms of bird flu?

The H5N1 can infect many animals, from birds to cows to even household cats. It can infect humans as well. In humans, there is a long list of symptoms that can present if the person contracts influenza from H5N1.

On December 18, the Department of Public Health for Los Angeles county published a notice that H5 bird flu was confirmed to have infected two household cats, with more cats suspected. The animals reportedly contracted the virus after consuming recalled milk. Currently, people who have been in contact with the cats are being monitored for signs of the disease.

According to the agency, those symptoms include:

• eye redness or discharge
• cough
• sore throat
• runny or stuffy nose
• diarrhea
• vomiting
• muscle or body aches
• headaches
• fatigue
• trouble breathing
• fever

How many people have become sick from bird flu?

CDC data shows that as of December 18, there have been a total of 61 confirmed human cases of H5 bird flu in the United States throughout 2024.

One of the most recent cases, which the CDC confirmed last week, is the one mentioned above: an individual who has come down with severe illness after contracting the disease. This individual is located in Louisiana, and their case “marks the first instance of severe illness linked to the virus in the United States,” according to the agency.

When it comes to human cases, 61 infections have occurred in eight states. California is the state with the most cases, followed by Washington and Colorado. The number of human cases in all impacted states is:

• California: 34
• Washington: 11
• Colorado: 10
• Michigan: 2
• Louisiana: 1
• Missouri: 1
• Oregon: 1
• Texas: 1

How far has bird flu spread in America?

In humans, bird flu has so far spread to the eight states listed above. However, the H5N1 virus in America is far more widespread. The CDC says that as of December 17, H5N1 has infected 10,852 wild birds in 51 jurisdictions.

As of December 18, the virus has infected over 123 million poultry in all 50 states. Also, as of December 18, the virus has infected 865 dairy herds in 16 states.

The Louisiana case that resulted in severe illness requiring hospitalization is believed to have occurred after the patient came into contact with dead and sick birds in backyard flocks. The CDC says this was the first case in the country where the illness has been linked to exposure to a backyard flock.

How does the H5 bird flu spread?

The CDC says that infected birds shed the H5 bird flu virus through their feces, saliva, and mucous. This means the virus can be contracted from not just the birds but also the surfaces they defecate on, the feed, and other sustenance they eat.

Other animals can shed the virus in respiratory secretions and via their bodily fluids—including in unpasteurized milk.

What can I do to avoid bird flu?

The CDC has a list of best practices to help someone from becoming infected with the H5 bird flu. They include:

• Avoid the consumption of raw milk and raw milk products.
• Avoid direct contact with wild birds.
• Avoid contact with sick or dead birds and any surfaces they may have come into contact with.
• Avoid unprotected exposure to sick or potentially sick cattle and any materials or surfaces they could have infected.
• Properly cook all poultry products you consume.

You can see the CDC's full list of recommendations here.

Is this the start of another pandemic?

Many of us remember the ominous reports of a flu-like disease popping up in December of 2019. Just three months later, the world was facing a global pandemic.

Thankfully, at this time, there are no signs that the H5 bird flu will deliver another global pandemic to our doorsteps. A big reason for that is that right now, the CDC says there has been no person-to-person spread of the virus. That’s not to say that can’t happen, nor will it stay that way, but for now, human-to-human transmission isn’t known to have occurred.

Of course, viruses continually mutate, and there is no guarantee that the H5 bird flu will never mutate into something far more transmissive in the future.

The CDC classifies the current public health risk of the virus as “low.”