Background

Avian influenza, commonly known as bird flu, refers to various strains of influenza A viruses. These viruses mainly affect wild birds but can also infect domestic birds such as poultry and pets. Some mammals may also be susceptible to certain strains, like H5N1, although they usually experience milder symptoms. There is a risk that humans could contract bird flu.

Current Situation

Over the past few years, public health departments at the federal, state, and local levels have been tracking a specific strain of Influenza A (H5N1) due to its ability to infect mammals. This includes wild animals like foxes, bears, and sea lions, as well as domestic pets such as cats and dogs. In 2022, a human case of H5N1 was detected for the first time in the United States in an individual who had direct contact with presumably infected poultry (see the full report).

More recently, in March 2024, H5N1 was detected in dairy cattle in the United States. This detection represents the first time H5 has been documented to infect cattle. In August 2024, H5N1 was detected in dairy cows in California for the first time.

There have been a small number of human infections associated with the ongoing H5N1 outbreak. Human infection with avian influenza is rare but expected. People who have direct contact with infected poultry or cattle are most at risk of infection. (see CDC's Current Situation Summary for details).

Despite these occurrences, the risk to the general public remains low. Human cases are extremely rare, and the virus typically does not spread from person to person. Those at greatest risk include individuals working with or living near infected birds or cattle.

In response, the Los Angeles County Department of Public Health is vigilantly monitoring H5N1 infections among domestic and wild birds, dairy cattle, and other mammals. The department is also collaborating with the Centers for Disease Control and Prevention (CDC) and the California Department of Public Health (CDPH) to ensure prompt identification and testing of any potentially exposed individuals who show symptoms.

Human H5N1 infections are very rare and we're still learning about how this virus might cause infection in mammals. The following are general best practices to prevent the spread of H5N1:

• Do not eat raw milk, raw cheese and undercooked meat products.
• Avoid unprotected contact with sick or dead animals. The virus can spread to other birds, pets or mammals if they come in contact with infected feces or eat infected animals.
• Report sick or dead birds to your local animal control agency for potential collection and testing. Sick birds or animals may not have flu-like symptoms, but may appear generally sick, have difficulty moving, seizures, or be found dead.
• Anytime you are in contact with animals, wash your hands with soap and water before touching your face or eyes.
• If you work with or around sick animals, use appropriate personal protective equipment.
• Prevent wild birds from getting into areas that house pet birds or poultry. Also make sure wild birds cannot defecate down into areas holding pet birds or poultry.
• Take down bird feeders and shared bird baths to reduce the risk of the virus spreading from bird-to-bird.
• Keep pets away from sick and dead birds as there is some risk of the virus spreading to dogs, cats and other wild mammals if they eat raw or uncooked poultry.
• Do not feed raw milk or raw milk products to pets.
• Get a seasonal flu vaccine. Seasonal flu vaccination will not prevent infection with avian influenza viruses but can reduce the risk of getting sick with human and bird flu viruses at the same time.

Information for the Public

Providers should be vigilant in evaluating patients presenting with influenza-like illness (ILI) or acute respiratory infection (ARI) symptoms who have had recent direct or close contact with birds or dairy cattle.

Suspected cases of novel influenza A virus infection warrant immediate collection of respiratory specimens.