The state health department says certain parts of Mexico have been active with the the mosquito borne Zika virus.
Those areas include Ensenada, Cabo San Lucas, and Sonora, which borders Arizona.
Health officials say the warning is going out to use mosquito repellent, wear long sleeves and don't have unprotected sex.
Zika is spread through mosquito bites and sexual transmission.
Condoms will help reduce the chance of sexual transmission of the virus, but if someone is thinking of getting pregnant they should use another form of contraception as well.
There haven't been any cases of the Zika virus being transmitted in the state of California, but San Diego has had 86 cases of people bringing back Zika from a trip.
Read the release from the state HERE.
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