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Zoonotic & Vectorborne

Zoonotic diseases are infections that humans catch from animals. They can be caused by viruses, bacteria, parasites and fungi.

People catch zoonotic diseases by coming in close contact with body fluids, such as blood, saliva or waste, from infected animals. These diseases also reach people through foods such as unpasteurized milk, undercooked meat and unwashed fruits and vegetables.

Common zoonotic diseases include influenza (flu), salmonellosis and E. coli (food poisoning). Diseases such as rabies and anthrax are also zoonotic.

Vector-borne diseases are passed to humans through bites from mosquitoes, ticks and fleas. Taking steps to prevent bites and reduce the local populations of these “vectors” is the best way to avoid these diseases.

  • Lyme disease –In California, the western black-legged tick carries the bacterium that causes Lyme disease. They are common in coastal regions, including Contra Costa County, and the Sierra Nevada mountain range.
  • West Nile – In Contra Costa County, some mosquitoes carry West Nile virus. It is the only disease passed to people from mosquito bites in our county.

Some vector-borne diseases are more common in other parts of the world, and can be caught by people traveling in those places. These are travel-associated or (imported):

  • Dengue is spread by a mosquito species in the tropics and subtropics. It is rare to catch dengue in the United States except in places where the Aedes mosquito lives, such as Puerto Rico and the U.S. Virgin Islands.
  • Malaria is caused by a parasite passed to people by another tropical mosquito species (Anopheles). Malaria is not spread in the United States, but is a major health problem in many parts of the world.

The Contra Costa Mosquito & Vector Control District offers free services and advice about mosquitos and other vectors at or 925-771-6196.