RIO DE JANEIRO—A top Brazilian health official warned pregnant women to think twice before giving a kiss as global measures mounted Friday against the Zika virus suspected of a link to birth defects.

The U.N. human rights agency called for some nations to loosen strict laws against abortion, and U.S. health authorities recommended that men who have visited areas with the Zika virus use condoms if they have sex with pregnant women.

Meanwhile, Colombian health officials said three people had died of Guillain-Barre syndrome after contracting the Zika virus. The country’s National Health Institute director, Martha Lucia Ospina, said all three victims were confirmed to have been infected with Zika. Still, most international experts are cautious about whether Zika can trigger the rare syndrome, which can cause complete paralysis, because other infections and conditions can lead to the illness.

In Rio de Janeiro, Paulo Gadelha, president of the Fiocruz research institute, told a news conference that scientists have found live samples of the virus in saliva and urine samples, and the possibility it could be spread by the two body fluids requires further study.

He said that calls for special precaution to be taken with pregnant women, and suggested they avoid kissing people other than a regular partner or sharing cutlery, glasses and plates with people who have symptoms of the virus.

“This is not a generalized public health measure, for the love of God,” he added, stressing both the seriousness of the discovery and reality that it was too soon to say how it could impact the epidemic.

Friday’s announcement coincided with the start of Carnival, a five-day-long bacchanal that sees millions of people take part in non-stop, alcohol-fueled parties where kissing as many people as possible is a top pastime. Gadelha underscored that the discovery needn’t alter Carnival plans for anyone but pregnant women.

Gadelha also stressed that the Aedes aegpyti mosquito, which also spreads dengue, chikungunya and yellow fever, remains the virus’ main vector and said the fight against the mosquito should be a top priority.

The Fiocruz team studied samples taken from two patients who showed symptoms of Zika and also tested positive for the illness. Tests on cell cultures showed the viruses in the samples were capable of damaging the cells, meaning that the viruses were active.

Myrna Bonaldo, who headed the Fiocruz team behind the discovery, said she was particularly surprised the virus was found in urine because Zika is generally thought not to thrive in acidic mediums.

“Each discovery is a surprise and a new find for us,” she said. “For us scientists, it’s extremely challenging to understand Zika virus.”

Meanwhile in Geneva, spokeswoman Cecile Pouilly said the U.N. High Commissioner for Human Rights was asking governments in Zika-affected countries in Latin America and the Caribbean to repeal any policies that restrict access to sexual and reproductive health services, including abortion.

“How can they . . . not offer (women) . . . the possibility to stop their pregnancies if they wish?” she said.

Pouilly gave the example of El Salvador, where about a quarter of women had experienced physical or sexual violence in the past year.

“So that also shows that many of these pregnancies are out of their control and countries obviously have to take that into account,” she said. Pouilly said that safe abortion services should be provided to the full extent of the law. “The key point is that women should have the choice and (make) informed decisions,” she said.

The National Conference of Bishops in Brazil, the South American country hardest hit by Zika, had no immediate comment on calls to loosen abortion laws. However, in a statement issued Thursday, the bishops said that the World Health Organization’s declaration earlier this week that Zika was an international emergency didn’t justify abortion.

Meanwhile, U.S. health officials said men who have visited an area with Zika should use condoms if they have sex with a pregnant woman — for the entire duration of the pregnancy.

The guidance issued Friday also says men might consider abstaining or using condoms even if they have sex with a woman who isn’t pregnant.

Zika virus disease is mainly spread by mosquitoes. But U.S. health officials detected a case of sexual transmission of the disease in Texas this week and in Brazil, officials said they had confirmed the virus was contracted via blood transfusions. For most people who catch the virus, it causes mild or no symptoms.

Officials previously recommended pregnant women postpone trips to more than two dozen countries with Zika outbreaks, mostly in Latin America and the Caribbean. Several Latin American nations have urged women to postpone pregnancies.

To date, the mosquito-borne virus has spread to more than 20 countries in the Americas, including some where sexual violence is rampant.

Brazil responded to complaints it had been slow to share data about the illness. In a statement Friday to The Associated Press, the health ministry said that it’s sending a set of Zika samples to U.S. health authorities. It did not immediately respond to requests for more details.

The announcement comes after the AP revealed that international health officials were frustrated at Brazil’s refusal to share enough viral samples and other information to answer the most worrying question about the outbreak: Whether the disease is truly causing a spike in babies born with microcephaly, or abnormally small heads.