Rio Carnival
Rio CarnivalReuters

Brazilian scientists, after having found the Zika virus in patients' saliva and urine, have advised pregnant women in the country to refrain from kissing strangers, especially during the Rio Carnival that kicked off on Friday. 

Brazil is reeling under its biggest outbreak of the Zika virus, which is being linked to rising cases of microcephaly -- a condition in which babies are born with abnormally small heads due to incomplete brain development. More than 4,000 cases of microcephaly have been reported in Brazil since last year. 

Scientists at Brazil's Oswaldo Cruz Foundation, for the first time, found active Zika virus present in saliva and urine samples of patients, using genetic testing, Reuters reports. 

The five-day Carnival that began in Brazil on Friday will see revellers indulging in drinking and street parties, and many are also known to participate in games that include kissing complete strangers. 

"In light of the possibility of being in contact with someone who is infected, do not kiss, obviously," Dr Paulo Gadelha, the president of the Brazilian institution, said on Friday. 

While it has not been proved yet that the virus can be transmitted through saliva, the Brazilian scientists said, "We cannot say today that there is no possibility of transmission."

The mosquito-borne Zika virus was also found to be spreading sexually, and the Centres for Disease Control and Prevention in the United States had this week advised pregnant women to avoid sex with men who had travelled to countries affected by the virus.

The virus has spread to over 23 countries in Latin America and the Caribbean, with several cases also being reported in the US and Europe. The World Health Organisation on Monday declared the virus a global public health emergency. 

The Rio Carnival is among the biggest events in the world and is expected to see about five million people join in. 

Concerns have also grown over the upcoming Rio Olympics in August, as the event is expected to bring lakhs of athletes and spectators to Brazil from around the world.