Returning travelers infected with Zika can spread the virus through mosquito bites and sex.
Even if they do not feel sick, travelers returning from an area with risk of Zika should take steps to prevent mosquito bites for 3 weeks so they do not spread Zika to uninfected mosquitoes. If a mosquito bites a person while he or she has Zika virus in his or her blood, the mosquito can become infected and then infect other people.
Couples with a partner who lives in or has traveled to an area with risk of Zika, especially those who are pregnant or planning to become pregnant, should take steps to protect during sex. Zika can stay in semen for months after infection (even without symptoms), and can be spread to partners during that time.