The head of a top Brazilian health research institute said its scientists have discovered the presence of the active Zika virus in urine and saliva samples.
Paulo Gadelha said at a press conference on Friday that the virus' ability to infect other people through the two body fluids requires further study.
However, he noted that the discovery calls for special precaution to be taken with pregnant women. Brazilian researchers have pointed to a suspected link between pregnant women's infection with the virus and a rare birth defect in babies.
The discovery does not yet merit any additional health recommendation, added Gadelha.
After confirming that the first case of the Zika virus was in a non-traveler in the continental United States, the Centers for Disease Control and Prevention issued new guidelines for pregnant women, and men with pregnant sex partners who have traveled to Zika-affected areas on Friday.
One of the new recommendations mentions that men with a pregnant sex partner who reside in or have traveled to an area of active Zika virus transmission and their pregnant sex partners should consistently and correctly use condoms during sex or abstain from sexual activity for the duration of the pregnancy.
The CDC also provided updated guidance for health-care providers who are caring for pregnant women to include a recommendation that even those without the symptoms of the Zika infection should be tested after returning from areas affected by the outbreak.
The suspected link between the Zika virus and a birth defect known as microcephaly appears "stronger and stronger" as researchers study whether there is a causal connection, CDC Director Tom Frieden said on Friday.
"I wish we knew more about Zika today. I wish we could do more about Zika today," said Frieden. "I understand that this is a stressful situation for women and families."
In response to the reported discovery of the Zika virus in urine and saliva, Frieden said that the CDC would need more information in order to provide further guidance.
"The bottom line is this is a mosquito-borne disease," Frieden told reporters.
In the continental U.S., there have been about 50 cases of travelers who were diagnosed with the Zika virus, including three pregnant women.
Since there is no vaccine or specific drug to treat Zika, stopping travel to locations that have Aedes mosquitoes is the primary form of preventing the virus from spreading to the United States.
To stop the further spread of the virus, the CDC has issued a travel alert to 30 countries and territories, which include popular vacation destinations such as Puerto Rico, Mexico and Barbados.
"Zika is a virus that can be spread in so many different ways," said Dr. Fiona Gupta, a neurologist at the North Jersey Brain and Spine Center. "We still have a lot to do before we truly understand it."
If people are living in places with Aedes mosquitoes, they are advised to use insect repellent, wear long-sleeved, light-colored clothes, and use insect screens or mosquito nets while inside. To help control the mosquito population, people should cover domestic water tanks, unblock drains, avoid accumulating garbage and avoid allowing water to stagnate in outdoor containers such as flower pots.
"I am encouraging my patients to exercise their judgment and caution before traveling. The higher-risk patients should really avoid going to the affected areas at all costs," said Gupta. "The virus is totally out of control right now."
— The Associated Press contributed to this report.