Aedes aegypti mosquito larvae sit in a petri dish at the Fiocruz institute in Recife, Pernambuco state, Brazil, Wednesday, Jan. 27, 2016. AP File Photo
MIAMI, United States鈥擴S health authorities are investigating 14 new cases of Zika virus that may have been transmitted sexually, suggesting a larger role than previously considered for the spread of the mosquito-borne virus.
Several of the cases involve pregnant women, the US Centers for Disease Control and Prevention warned Tuesday.
The agency reiterated its call for people to use condoms or practice abstinence when living in or traveling to the more than 20 nations and territories in Latin America and the Caribbean affected by the Zika virus.
The virus is suspected to have played a role in a spike of birth defects in Brazil.
鈥淚n all events for which information is available, travelers were men and reported symptom onset was within two weeks before the non-traveling female partner鈥檚 symptoms began,鈥� the CDC report said.
鈥淭hese new reports suggest sexual transmission may be a more likely means of transmission for Zika virus than previously considered.鈥�
Experts still consider Zika a primarily mosquito-borne virus, and urge people to avoid bites by applying insect repellent, using bed nets and wearing long sleeves and pants.
The United States reported its first case of sexually transmitted Zika virus in early February, after a man traveled to Venezuela then returned to Texas and聽infected a partner who had not traveled there.
READ: As Zika spreads, Texas reports sexually transmitted case
鈥淚n two of the new suspected sexual transmission events, Zika virus infection has been confirmed in women whose only known risk factor was sexual contact with an ill male partner who had recently traveled to an area with local Zika virus transmission,鈥� said the CDC.
鈥淭esting for the male partners is still pending.鈥�
The CDC said the 14 cases, 鈥渓ike previously reported cases of sexual transmission鈥� involve possible transmission of the virus from men to their sex partners.鈥�
Health officials currently have 鈥渘o evidence that women can transmit Zika virus to their sex partners; however, more research is needed to understand this issue.鈥�
READ: US Zika case sparks questions about sex and mosquito germs
There is no vaccine to prevent Zika virus and no medicine to treat it.
In four out of five cases, people who are bitten by an infected mosquito show no symptoms.
Otherwise, symptoms may include a rash, red eyes and a headache.
But in pregnant women, the consequences could be dire.
Scientists are currently trying to figure out if Zika could have caused an increase in birth defects in Brazil, where thousands of babies have been born with unusually small heads since the virus began to spread there.