Brazil vows worry-free Olympics

"The situation does not compromise the Olympics," Rousseff said as she joined soldiers in a nationwide campaign to teach citizens how to fight the outbreak.

"We are confident that by the time the Olympics begin we will have considerable success in exterminating the mosquito" known as Aedes aegypti that transmits the virus, she added.

Rio de Janeiro will host the Summer Games August 5 to 21, drawing athletes and spectators from around the world.

Brazil has been most affected by the outbreak that has spread rapidly through Latin America and the Caribbean, with 1.5 million people in the country infected since early 2015.

It has confirmed three deaths linked to the virus.

While it causes only mild flu-like symptoms in most people, Zika is strongly suspected of a rapid rise in the number of children born with microcephaly -- abnormally small heads and brains -- to mothers infected during pregnancy.

Several countries have urged women to avoid getting pregnant as researchers work to confirm whether Zika causes microcephaly and the neurological disorder Guillain-Barre syndrome.

- 'War' on Zika mosquitoes -

Rousseff spoke to reporters after visiting houses in a poor neighborhood of Rio de Janeiro as part of the national anti-Zika campaign.

Early Saturday, some 220,000 soldiers fanned out across the vast South American country, part of an operation aiming to knock on three million doors and distribute informational leaflets.

Warning that pregnant women were especially at risk, Rousseff urged all Brazilians to come together.

"The war depends on us," she said, accompanied by officials, health workers and a swarm of journalists.

Wearing a white cap and short-sleeve shirt with the slogan #ZikaZero, the president personally sprayed larvicide in areas where mosquitoes can breed.

"The government is taking the lead but that alone won't win the war," she said. "We need to get everyone involved."

- Country mightier than mosquito -

Visiting homes, restaurants and shops, military personnel handed out leaflets with the slogan "a mosquito is not stronger than an entire country."

They advised residents to keep water tanks tightly covered, turn open bottles upside down and store tires in places where they won't collect water.

Several government ministers accompanied troops in other major cities including Salvador, Recife, Curitiba and Porto Alegre.

According to the latest data from Brazil's health ministry, the country recorded 462 cases of microcephaly between October and February, compared with an annual average of 150 cases. 

Forty-one of the cases have a confirmed link to the Zika virus. Another 3,852 suspected cases were being studied.

One of Brazil's top health officials, meanwhile, warned that Zika was likely to spread to densely populated areas -- including Rio and Sao Paulo. 

"This is the great fear of the immediate future -- that densely populated states will experience an intense outbreak of the virus that cannot be controlled," Claudio Maierovitch, head of the communicable diseases surveillance department at the health ministry, told AFP.

- Colombia reports new cases -

In the second worst-affected country, Colombia, health authorities on Saturday reported 31,555 cases of Zika, of which just over 5,000 were pregnant women. 

For this year, they are forecasting 600,000 Zika cases overall and about 500 cases of microcephaly.

There is currently no cure or vaccine for Zika.

However, the US ambassador to Bogota said Friday that American scientists have traveled to Colombia to research a vaccine.

The World Health Organization has declared the rise in Zika-linked birth defects an international emergency.

AFP