MONTEVIDEO (AFP) - South American health ministers launched emergency talks Wednesday on fighting the fast-spreading Zika outbreak after a US case of sexual transmission of the virus, which has been blamed for brain damage in babies.

Ministers from 13 countries including the two reportedly worst affected, Brazil and Colombia, gathered in Uruguay to coordinate their fight against the mosquito-borne illness which authorities fear may spread worldwide.

Arriving at the meeting in Montevideo, Brazil's Health Minister Marcelo Castro told reporters his country had deployed 522,000 personnel to prevent infections by cleaning up and advising the population.

He called it "the biggest effort in Brazil's history." Brazil has reported 1.5 million cases of infection by Zika, more than any other country.

The fever starts with a mosquito bite and normally involves little more than a fever and rash.

But scientists suspect that when it strikes a pregnant woman, it can cause her fetus to develop microcephaly - a condition which causes the baby to be born with an abnormally small head.

Since October, Brazil has reported 3,670 suspected cases of microcephaly, of which 404 have been confirmed - up from 147 in 2014.

Doctors have also linked it to a potentially crippling neurological disorder, Guillain-Barre syndrome.

Alarm bells rang on Tuesday when authorities in Texas said they had confirmation of the virus being transmitted by sexual contact and not just tropical mosquitoes.

Dallas County officials said a patient there was infected following sexual contact with someone who had returned to the United States after contracting it in Venezuela.

The World Health Organisation (WHO) has declared the spike in serious birth defects in South America an international emergency and launched a global Zika response unit.

Colombia, Ecuador, El Salvador, Jamaica and the US territory of Puerto Rico have all warned women not to get pregnant.

Brazilian authorities are on alert over the threat to the Olympic Games to be held in in Rio de Janeiro in August.

"We are sure we will win this battle and it will not affect the Games," Rio 2016 organising committee spokesman Mario Andrada said, however, on Tuesday.

The Olympics will be held during the southern hemisphere winter, which means there will be fewer mosquitoes, organisers stressed.

WHO expert Anthony Costello emphasised the urgency of rapid action, stressing there was no reason to believe the crisis would remain limited to Latin America.

"We know that the mosquitoes that carry Zika virus... are present through most of Africa, parts of southern Europe and many parts of Asia, particularly south Asia," he said.

Health experts have warned that Zika poses a massive threat to Asia, with its rampant mosquitoes and a history of rapidly spreading infections.

Thailand confirmed on Tuesday that a man contracted the infection and Indonesia has also reported a domestic case.

Officials in India worry it could be next, noting that the Zika and dengue fever-carrying Aedes aegypti mosquito thrives in its teeming cities.

Cape Verde off north-west Africa has also detected a case of Zika.

The WHO on Wednesday warned European countries to act early to prevent the spread of Zika.

According to the European Centre for Disease Prevention and Control (ECDC), the mosquito has "re-colonised" Madeira in Portugal and parts of Southern Russia and Georgia in recent years after disappearing from the continent in the 20th century. It has been spotted as far north as the Netherlands.

The International Federation of Red Cross and Red Crescent Societies joined the WHO in declaring an "emergency," and appealed for US$2.36 million (S$3.3 million) to support its response in the Americas.

French pharmaceutical giant Sanofi announced it had begun research into a vaccine for Zika, for which there is currently no specific treatment.

Developing a vaccine could, however, take years, experts say.

Wednesday's meeting in Uruguay involved delegates from Argentina, Bolivia, Brazil, Colombia, Costa Rica, the Dominican Republic, Ecuador, Mexico, Paraguay, Peru, Suriname, Uruguay and Venezuela.

It was also attended by a delegation from the Pan American Health Organisation.

A press conference was scheduled for 1700 GMT (1am Singapore time).