Pregnant women should not kiss anyone other than a regular partner, Brazil health officials warned in a sign of growing concern over the Zika virus.

They were also told to avoid sharing cutlery, glasses and plates with people who have symptoms of the virus, while men were warned to use condoms with pregnant partners if they have visited countries where the virus is present.

UN officials called on many Catholic-majority countries in Latin America to loosen their abortion laws to allow women to terminate pregnancies if they fear the foetus may be at risk of a rare birth defect that causes brain damage and an abnormally small head, which may be linked to the virus.

In Brazil, Paulo Gadelha, president of the Fiocruz research institute, said that scientists have found live virus in saliva and urine samples, and the possibility it could be spread by the two body fluids requires further study.

He urged pregnant women to take special precautions, stressing both the seriousness of the discovery and the reality that it was too soon to say how it could impact on the epidemic.

"This is not a generalised public health measure, for the love of God," he said.

Friday's announcement coincided with the start of Carnival, a five-day event that sees millions of people take part in alcohol-fuelled parties where kissing as many people as possible is a popular pastime.

Mr Gadelha said the discovery need not alter Carnival plans for anyone but pregnant women.

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