The current avian influenza outbreak led to the infection of 66 people in 10 states in 2024, CDC records show. Most cases, 36, were in California and tied to dairy cattle exposure. Washington and Colorado reported 11 and 10 human infections, respectively, primarily linked to poultry farms. One person has died, the Louisiana Department of Health confirmed Jan. 6. The deceased, an adult over 65 with underlying medical conditions who had been hospitalized after exposure to wild birds and a non-commercial backyard flock, remained the sole H5N1 case in the state.

Of course, the birds have it worst. The Department of Agriculture’s Animal and Plant Health Inspection Service confirmed the virus in nearly 11,000 wild bird samples between Jan. 1, 2022, and Jan. 3, 2025. More than 130 million birds from over 1,300 backyard and commercial poultry flocks have been infected since Feb. 8, 2022. Mammals haven’t been spared. Last year alone, more than 900 cattle tested positive. What’s more, wild mammals from bobcats to brown bears have caught the ailment.

The good news—for now—is that the CDC hasn’t detected any person-to-person spread and says avian influenza’s current risk to public health is low. That could change if not enough people get their seasonal flu shot.

The potential for danger lies in H5N1’s genetic pliability, according to Edwin Michael, PhD, an epidemiologist at the University of South Florida College of Public Health.

“For example, if a human gets infected with a bird flu and also carries a human influenza A virus, these two viruses can exchange genetic material. This is known as genetic shift,” Michael previously told Fortune. “That can form very new viruses [and] cause epidemics.”

Immunization reduces the prevalence and severity of seasonal flu, the CDC says, thereby reducing the “very rare” but possible risk of coinfection, “which could pose a significant public health concern.”

The CDC particularly recommends the flu shot for people who may have frequent exposure to infected or potentially infected birds or other animals. Keep in mind that it takes your body up to two weeks after vaccination to achieve immunity.

Is it too late to get a flu shot?

Don’t worry if you missed the unofficial “vaccine before Halloween” memo. We’re in the thick of cold and flu season and any protection you can provide yourself, your loved ones, and your community will benefit public health, says Dr. Robert Hopkins Jr., medical director of the National Foundation for Infectious Diseases.

“It’s not too late,” Hopkins told Fortune in December. “It is not a bad time when we’ve got risk in front of us. And I would certainly prefer that people were vaccinated earlier, but I’m not going to make perfection the enemy of the good.”

In the U.S., about two in five adults (41.7%) and two in five children (42%) had gotten their seasonal flu vaccine as of the week ended Dec. 14, according to the CDC, whose Healthy People initiative aims for a 70% immunization rate. The rate for adults is about what it’s been during the same week the previous three seasons. Children, however, had their lowest flu vaccination rate in the past six seasons. By comparison, more than half of children (53.1%) had been vaccinated by that week in the 2019–20 season.

Daniel Chetroni—Getty Images

Will there ever be a bird flu vaccine?

Should H5N1 bird flu begin to spread from person to person and lead to a pandemic, an effective vaccine may arrive sooner than later.

As part of its pandemic preparedness protocols, the CDC says it routinely develops candidate vaccine viruses (CVVs) that pharmaceutical companies can use to engineer immunizations. The agency has already prepared CVVs closely matching the type of bird flu currently circulating, which “could be used to produce a vaccine for people, if needed.”

For more on bird flu:

• Can you get bird flu from eating eggs? What you need to know about staying safe
• Experts sound the alarm as Ohio farmworker’s bird flu sparks fear it’s the next pandemic
• Bird flu FAQ: Everything you need to know about the latest H5N1 outbreak
• What are the symptoms of bird flu and how does it spread?
• USDA orders nationwide testing of milk for bird flu to contain and eventually eliminate the virus