Avian Flu

Every winter, millions of migratory birds fly south to warmer locales, passing over California Central Valley dairies and poultry farms. Many of these wild waterfowl are carrying the virus that causes avian influenza, based on the U.S. Department of Agriculture's wild-bird surveillance, says Maurice Pitesky, University of California Cooperative Extension poultry specialist in the School of Veterinary Medicine at UC Davis.

The sounds of barking elephant seals are again in the air along the breeding grounds of Península Valdés, Argentina—but it’s quieter. Roughly a year after a massive outbreak of H5N1 highly pathogenic avian influenza killed more than 17,000 elephant seals, including about 97% of their pups, scientists estimate that only about a third of the elephant seals normally expected here returned.

As highly pathogenic avian influenza (HPAI) continues to spread throughout the world, including on California dairy farms recently, experts on the subject from the UC Davis School of Veterinary Medicine have taken great strides to educate the public and industry partners on the subject.

Since 2022, a new, highly pathogenic strain of H5N1 influenza or “bird flu” has spread worldwide. In the U.S. it has affected over 100 million birds and for the first time, spread into dairy cows and a small, but growing, number of people. At UC Davis, experts in One Health — an approach that considers the health of people, animals and the environment together — are on high alert.

Dead silence met Marcela Uhart and her team when they arrived at the elephant seal colony at Punta Delgada, Patagonia on Oct. 10, 2023.

The discovery of fragments of avian flu virus in milk sold in U.S. stores, including in about 20% of samples in initial testing across the country, suggests that the H5N1 virus may be more widespread in dairy cattle than previously realized.

A poultry expert at the UC Davis School of Veterinary Medicine (SVM) has teamed up with a geographic information systems (GIS) expert at UC Agriculture and Natural Resources (ANR) and two wildlife health experts from the UC Davis SVM Wildlife Health Center (WHC) to create a map showing the spread of highly pathogenic avian influenza (HPAI) since 2021.