A fresh outbreak of bird flu, classified as highly pathogenic avian influenza, has been identified in California.

The newly identified H5N9 strain was detected on a duck farm in Merced County, California, on Monday, as per the World Organization for Animal Health. This Paris-based agency focusing on animal diseases announced it is the first confirmed case of H5N9 in U.S. poultry. Notably, the more prevalent H5N1 strain has also been discovered.

With the ongoing rise in bird flu cases across the U.S., entire poultry farms have been eradicated in efforts to manage the spread of the virus.

Human Cases of Bird Flu in the U.S.

As of now, 60% of human cases have arisen from contact with infected birds through cattle, according to the Centers for Disease Control and Prevention (CDC). About one-third of these instances are related to culling activities or exposure to chicken farms. Out of over 600 individuals who had contact with infected animals, 67 have tested positive for the illness since 2024.

One individual succumbed to the bird flu on January 6 in Louisiana. The patient was over 65 and showed symptoms after coming into contact with a mix of backyard chickens and wild birds, as reported by the Louisiana Department of Public Health.

Effects of Bird Flu on U.S. Poultry Farms

Over the past three years, bird flu cases have been reported involving more than 145 million birds across 618 counties nationwide, according to CDC data as of January 24.

The CDC suggests that people including backyard flock owners, hunters, and bird lovers should take additional precautions if they interact with or engage in recreational activities involving birds or farm animals.

Impact on Cattle Farms in the U.S.

The bird flu has also affected dairy cattle throughout the United States, resulting in several human cases. From October to December 2024, as bird infections surged, the majority of cattle cases – 673 out of 929 – tested positive for the virus, according to USAFACTS.

States Affected by Bird Flu in Cattle Herds

Since early 2024, 77% of all recorded avian flu cases in cattle have been in California.

What Are the Symptoms of Bird Flu in Humans?

Although it’s still rare for avian flu viruses to infect humans, the disease can be transmitted through the mouth, eyes, or nose. In some instances, individuals have inhaled the virus after interacting with an infected animal.

◾ Mild Symptoms: Fever, cough, sore throat, body aches, conjunctivitis (pinkeye), runny or blocked nose, fatigue, and muscle pain.

◾ Severe Symptoms: Difficulty breathing, high fever (100 degrees Fahrenheit or higher), pneumonia (which may necessitate hospitalization), and severe respiratory illness.

CONTRIBUTING Fernando Cervantes Jr. and Jim Sergent

SOURCE Centers for Disease Control and Prevention, U.S. Department of Agriculture, World Organization for Animal Health, Newsweek, USAFACTS.org, and YSL News research

This report was updated to incorporate new information.