CDC Confirms Two Human H5 Bird Flu Cases in California

The CDC confirmed two human cases of H5 bird flu in California on October 3, 2024, involving individuals with occupational exposure to infected dairy cows. According to the CDC, these are separate instances of animal-to-human spread with no known link between the two patients, and the risk to the general public remains low.

These represent the first human cases of H5 in California. The state first reported H5N1 outbreaks among dairy herds in August 2024, according to CDC data.

Why are H5 bird flu cases appearing in California?

The confirmed cases occurred in people working with infected dairy cows. CDC officials stated the identification of H5 in people exposed to infected animals is not unexpected.

H5N1 bird flu was detected in cows in the United States for the first time this year. The virus is already widespread in wild birds and has caused poultry outbreaks across the U.S. since 2022, according to the CDC.

Did You Know? H5N1 bird flu was detected for the first time in cows in the United States in 2024.

What is the current national risk and case count?

The CDC maintains that the risk to the general public is low. Including the California cases, 16 human cases have been reported in the U.S. during 2024, bringing the total to 17 cases since 2022.

Bird flu mutated inside US patient: CDC

The 2024 cases are distributed across five states: Colorado (10), Michigan (2), California (2), Texas (1), and Missouri (1). According to the CDC, six of the 16 cases this year linked to infected dairy cows, while nine linked to infected poultry.

One case in Missouri has an undetermined source of infection. The CDC is currently conducting serologic testing of contacts for that specific case.

Expert Insight: Samantha Carter notes that the lack of a known link between the two California cases is a critical detail. It suggests the virus is jumping from animals to humans in isolated events rather than spreading between people.

How can people protect themselves from H5N1?

The CDC recommends avoiding contact with wild birds and animals that are sick or dead. To prevent infection, the agency advises against preparing or eating raw cheese or unpasteurized (raw) milk.

Farm workers are urged to wear personal protective equipment (PPE) when around raw milk, dairy cows, or contaminated surfaces. The CDC recently issued updated PPE guidance to help prevent H5N1 bird flu infections.

What happens next in the investigation?

California is leading an ongoing investigation into these cases. The CDC is collaborating with state public health officials to control the spread of the virus from animals to humans.

In the coming days, the CDC may isolate and grow the viruses. The agency will also conduct additional characterization, including sequencing of the viruses, if possible.

Identifying H5 Symptoms

The CDC recommends contacting a health care provider and local health department for testing if symptoms appear after close animal contact. Symptoms include eye redness (conjunctivitis), fever, cough, and sore throat.

Other signs may include difficulty breathing, muscle aches, and a runny or stuffy nose, as well as mild flu-like upper respiratory symptoms.

Frequently Asked Questions

What are the symptoms of H5 bird flu in humans?

According to the CDC, symptoms include eye redness (conjunctivitis), fever, cough, sore throat, difficulty breathing, muscle aches, a runny or stuffy nose, and mild flu-like upper respiratory symptoms.

How many human H5 cases have occurred in the U.S. recently?

There have been 16 human cases reported in 2024, with a total of 17 cases since 2022, according to the CDC.

Who is most at risk for H5N1 infection?

The CDC reports that rare, sporadic infections have occurred in people who work with infected animals, specifically poultry workers and dairy cow workers.

Do you follow the CDC’s guidelines regarding unpasteurized dairy products?