Centres for Disease Control and Prevention (CDC) said it was investigating 14 new reports of possible sexual transmission of the Zika virus in the country.
The CDC said in a statement on Wednesday in Washington that several of the cases involved pregnant women.
It said it has earlier this month published an interim recommendation for protecting people against sexual transmission of the Zika virus.
The CDC said that in two of the new suspected sexual transmission events, Zika virus infection was confirmed in women whose only known risk factor was sexual contact with an ill male partner.
The reported noted that male partner had recently travelled to an area with local Zika virus transmission.
The CDC said further that four additional suspected sexual transmission events, preliminary laboratory evidence was available for the women, but confirmatory tests are pending.
“Eight other cases are still under investigation.
“In all events for which information is available, travelers were men and reported symptom onset was within two weeks before the non-travelling female partner’s symptoms began.
“Like previously reported cases of sexual transmission, these cases involve possible transmission of the virus from men to their sex partners,” it added.
The statement said further that it has released guidelines on preventing Zika sexual transmission, following lab confirmation of the first case of virus infection in a non-traveler in the continental U.S. who was linked to sexual contact with an infected partner.
The guidance recommended that men with a pregnant sex partner who have resided in or travelled to areas with the Zika virus should use condoms or abstain from sex for the entire duration of the pregnancy.
It, however, said although sexual transmission of Zika virus infection was possible, but mosquito bites remain the primary way that Zika virus is transmitted.
The CDC warned that currently there is no vaccine or treatment for Zika virus, the best way to avoid Zika virus infection is to prevent mosquito bites.