As California’s Central Valley makes headlines for the growing number of people testing positive for the bird flu from exposure to dairy cows, Rais Vohra, MD, professor at UC San Francisco, Fresno and interim health officer for the Fresno Department of Public Health (DPH), is in the eye of the storm. An emergency medicine physician, Vohra serves as the medical bridge between county health and farmers, and guides prevention protocols for Fresno and neighboring Tulare and Kern counties, where dairy and poultry farms have been directly impacted by the virus.
Vohra explains what we know about bird flu, both the H5N1 and H5N9 variants, and the precautions we can take to prevent it from becoming a public health emergency.
What is bird flu?
Bird flu originated as a common name for the H5N1 virus strain of influenza that has been affecting wild birds and poultry for decades. The H5N1 strain was originally seen in wild birds and poultry farms but made the jump from birds to mammals in a Texas dairy cattle ranch in March 2024 and is now knocking on the door of humans.
A new variant, H5N9, recently appeared in California. What should readers know?
Yes, a new bird flu variant was discovered at a duck farm in late January. It has the potential to be more virulent for birds and other farm animals. But, it’s important to know that it does not pose any greater risk to humans.
Health officials and scientists are monitoring H5N9 closely, however, because its evolution alongside seasonal flu and other strains, could, in the future, produce new versions of the virus that spread more easily among humans.
How many cases of the bird flu have we seen in the U.S. in 2024?
From April to mid-October, there have been 27 confirmed human cases of bird flu in the U.S. Thirteen of those cases were in California’s Central Valley.
How does it spread?
We know that this is a respiratory virus and is not bloodborne. It is spread by breathing air containing floating viral particles and from touching surfaces that may have the viral droplets, similar to the common cold.
Has there been any recorded instance of human-to-human transmission in the U.S.?
No.
Is it highly contagious?
So far, it is mainly contagious among poultry and dairy cows. Farmers who tested positive in California have all been in close contact with dairy cows, so all dairy farms in the Central Valley are on alert. None of the California patients were in contact with each other, nor did they transmit the virus to others in their household.
Is there a vaccine to protect people from the bird flu?
At this time, vaccines for the bird flu are in development and are being actively researched, but nothing is available to the public at this time.
Will the seasonal flu vaccine protect the public from the bird flu?
No, the seasonal flu vaccine will not protect patients from catching the bird flu. However, I strongly encourage everyone to get this year’s flu vaccine, especially those who work closely with dairy cattle or poultry farms. There is a concern among infectious disease experts that if a person with the common flu virus also becomes infected with the bird flu, the two viruses in the same body could combine into variants that will more easily spread through human contact.
Editor's note: This article has been updated with new information. It was originally published on Oct. 22, 2024.
What are the symptoms of bird flu?
The trademark symptom of bird flu infection is conjunctivitis or pink eye. When I’m consulted about a potential case of the bird flu, I ask two questions: Does the patient have pink eye, and Do they work in the dairy or poultry industry? For some reason, every person who has tested positive for bird flu has developed pink eye. Physicians think the virus may be attracted to that tissue in the human body.
Other symptoms include more traditional flu-like symptoms such as:
- Mild flu-like upper respiratory symptoms like congestion
- Pneumonia, possibly requiring hospitalization
- Fever (100ºF/37.8ºC or greater) or feeling feverish*
- Cough
- Sore throat
- Runny or stuffy nose
- Muscle or body aches
- Headaches
- Fatigue
- Shortness of breath or difficulty breathing
- Less common signs and symptoms include diarrhea, nausea, vomiting and seizures.
*Fever may not always be present
Can it be deadly?
Around the world, yes people have died from bird flu. Fortunately, that is not the case in the U.S.
Is UCSF Fresno providing medical outreach to the community for bird flu?
Yes. At the start of the COVID-19 pandemic, UCSF Fresno launched Mobile HeaL – an outreach effort for patients who do not have access to health clinics or medical care. Run by UCSF Fresno clinicians and funded by city and county grants, HeaL is an agile mobile unit that provides vaccinations, treatment and medications to homeless shelters, farm-based communities and other rural areas that don’t have regular access to health care services. The Mobile HeaL team is partnering with the Fresno DPH to plan a response to the bird flu, such as testing for bird flu, providing seasonal flu shots, COVID vaccines and prescriptions for Tamiflu (oseltamivir) for patients and their families if needed.
Can I get the bird flu from raw milk?
Bird flu can spread through unpasteurized, or raw, cow’s milk. All patients infected with the virus in California have been in close contact with handling raw milk from infected cows.
Can I get the bird flu from drinking milk from an infected cow?
In most cases, no. Cows are required to be regularly tested and milk from infected cows is required to be discarded. The general milk supply is safe because it has been pasteurized and only sourced from healthy cows.
Can you get bird flu from eating partially cooked chicken?
There is no indication that you can catch this virus from eating chicken. As always, we encourage people to only eat thoroughly cooked chicken.
Can you get bird flu from eating infected rare beef?
The bird flu does not spread through the meat of cattle.
