Aedes aegypti and Aedes albopictus can transmit several viruses to people when they bite, including dengue, chikungunya, Zika, and yellow fever. These viruses are widespread in other parts of the world, including in Mexico, Central and South America, the Caribbean, and Asia, but are not known to be currently found in mosquitoes in California. People traveling in areas where these viruses are present can become infected from mosquito bites. When they return to California, people that are infected can serve as sources for mosquitoes to become infected and pass the virus to others. In this way, limited local transmission of dengue virus has occurred in California.
Travelers can protect themselves and others by preventing mosquito bites. When traveling to areas with dengue, chikungunya, or Zika, use insect repellent, wear long sleeves and pants, and stay in places with window and door screens. It's also important to use insect repellent for three weeks after returning home to prevent the spread of viruses to Aedes aegypti and Aedes albopictus mosquitoes in California.