Authorities say thousands of migrating birds have died at California's Salton Sea this month from avian cholera.

The California Department of Fish and Game says ducks, gulls and other birds were found dead at the south end of the state's largest lake between Jan. 8 and last Thursday.

Testing showed signs of avian cholera, an infectious bacterial disease. It's spread through direct contact or from contaminated food or water.

Wildlife officials say outbreaks occur annually as a result of birds flocking closely together during migration.

The 350-square-mile (560-square-kilometer) lake is located in the desert near the Mexican border. It's a regular stop for migrating birds.

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