Many countries have raised their alert levels or boosted their efforts against the Zika virus as scientists race to develop a vaccine for Zika, but the World Health Organization (WHO) says vaccines could come out in at least 18 months.

Brazil, the center of the endemic, has been scaling up its efforts, including mobilizing troops, to curb the spread of Zika since it declared a public health emergency in November 2015.

The focus of fighting the virus has been on eliminating its carrier, the Aedes aegypti mosquito.

As the Olympic Games are scheduled for August in Rio De Janeiro, controversies have risen over the risk of holding the Games in the city.

Rio De Janeiro Mayor Eduardo Paes, however, brushed aside concerns for health risks on Friday, saying the Zika virus is not a threat to the Olympic Games.

"We have to deal with the Zika problem, but that is not an Olympic issue. It is an issue for us Brazilians and for Rio de Janeiro," he said.

Mayor Paes argued that August and July are in the dry season, with less incidence of the mosquito that usually lays its eggs on stagnant water.

But he vowed no letup in the fight. "We must take all the necessary precautions, show that we are doing whatever we can to prevent any athlete or visitor who comes to Rio from catching the disease."

Paes criticized the uproar over the Zika virus, saying there is "some exaggeration" about the risks.

The Brazilian Health Ministry have announced it would launch a national mobilization campaign to exterminate the Aedes aegypti mosquito in the country's 350 highly vulnerable cities.

Brazilian Defense Minister Aldo Rebelo said the latest campaign will go house to house, reaching at least 3 million homes and distribute 4 million leaflets on Saturday.

President Dilma Rousseff has sent her ministers to join the mobilization efforts in various states.

So far, over 4,000 cases of microcephaly in newborns have been registered in Brazil. Out of those, over 400 have already been confirmed.

So far, more than 500,000 people, including 222,000 soldiers, have been dispatched to help the mosquito eradication efforts in Brazil. They have already visited 23.8 million buildings nationwide, including private homes, public buildings and commercial properties.

So far, the Zika outbreak reportedly has affected more than 30 countries.

Colombia's national health institute on Saturday reported a total of 31,555 cases of the disease in the country, including 5,013 pregnant Colombian women infected with the mosquito-borne Zika virus, which continues its rapid spread across the Americas.

China confirmed its first imported case of the Zika virus on Tuesday, and its southwestern border province of Yunnan is on high alert, providing 24-hour laboratory tests for the virus.

Lu Lin, director of the Center for Disease Control and Prevention in Yunnan, said on Friday the center is able to obtain the test result in four hours.

He said the center has assessed risks of imported case of the Zika virus in all prefectures and cities in the province, which borders Myanmar, Laos and Viet Nam.

Zika drew the attention of the WHO after it was discovered that pregnant women infected by the virus were giving birth to an increasing number of babies with microcephaly, a syndrome characterized by a smaller cranium, often accompanied by other health problems and cognitive delays.

The WHO said on Friday that possible Zika vaccines are expected to come out for large-scale clinical trials in at least 18 months, advising pregnant women to delay travel to areas where the Zika virus had turned up.

The world health body also said the possible link between the Zika virus and microcephaly in some new born babies is expected to be confirmed within weeks.

(Xinhua News Agency February 14, 2016)