Zika virus has been identified in certain tropical and subtropical areas including but not limited to Mexico, the Caribbean, Africa, Central and Latin America, etc. It causes human disease and is most often spread by the bite of a particular species of mosquito common to such areas. There is evidence that Zika virus can also be transmitted sexually.
Although Zika infection can be so mild as to pass unnoticed, there is evidence that infection during pregnancy can lead to a small head and neurological damage in the newborn. The Centers for Disease Control (CDC) therefore recommends that pregnant women and those that might become pregnant during or immediately following travel to a Zika risk area should avoid or delay non-essential travel and follow other preventative measures, see Zika travel information.
Zika infection may also be associated with the risk of Guillain-Barre syndrome, another reason to follow CDC recommended preventative measures to reduce mosquito bites and sexual transmission. This is important for travelers to Zika infested areas and for those interacting sexually with someone that has recently been in an identified Zika risk area.
Periodically updated information about Zika virus, including travel, sexual transmission, the possibility of Zika carrying mosquitos in certain US warm climate areas, etc. is available from the CDC and CA Public Health Department.