Army soldiers in Rio de Janeiro set up a banner that reads in Portuguese “A mosquito is not stronger than a whole country.” (Silvia Izquierdo/AP)

More than 200,000 troops fanned out across Brazil on Saturday to raise awareness about the mosquito that spreads the Zika virus, which has been linked to a surge in birth defects.

Aiming to reach 3 million families in a single day, soldiers visited homes, parks and shopping malls in 350 cities, passing out pamphlets with instructions on how to prevent the accumulation of stagnant water, where the Aedes aegypti mosquito breeds. The effort, branded #ZikaZero, is part of a larger campaign by public health officials and the military to inspect buildings for stagnant water and treat potential breeding grounds with insecticides.

Marcelo Castro, Brazil’s health minister, said Friday that the government is “absolutely sure” that Zika is behind the country’s recent jump in cases of microcephaly, a condition where babies are born with unusually small heads. According to official statistics, 41 cases of microcephaly have been tied to Zika, and more than 3,800 cases are being investigated. As many as 1.5 million Brazilians may have been infected with the Zika virus.

Although the World Health Organization has yet to establish a definitive link between the virus and the rare birth defect, it is advising pregnant women to consider delaying travel to Brazil and other Latin American countries where the virus has spread. The outbreak also has raised questions about the safety of tourists and athletes at the Olympic Games, which will be held in Rio de Janeiro in August.

Highlighting these concerns, Brazilian President Dilma Rousseff joined health officials in Rio as they swept through the cinder-block shacks of a favela — one of the country’s many informal settlements typically marked by poor infrastructure and scant public services. Because they allow standing water to collect, these are ideal conditions for the Aedes aegypti to reproduce.

“In the past, we won the war against yellow fever, and we are going to win the war against the Zika virus,” Rousseff told reporters. “We’re trying to catch up after decades of abandonment in terms of sanitation.”

Rousseff championed her government’s investments in basic sanitation, but some blame the Zika outbreak on years of neglect of public services such as trash collection. According to Trata Brasil, a nonprofit organization that studies sanitation, fewer than half of Brazilians live in homes hooked up to sewage lines, and 35 million lack access to clean drinking water. Last year, the country reported 1.6 million probable cases of dengue, a virus also transmitted by the Aedes aegypti mosquito.

“The red flags were already there,” Marta Suplicy, a senator who recently left Rousseff’s party, said in an editorial published Friday. “The federal government is deploying the Armed Forces to assist in the fight against the mosquito that transmits the [Zika] virus. Very good. But the issue is deeper: If we don’t solve the structural problems, we will keep suffering setbacks.”

Luciano Pamplona, a biologist and the secretary-general of the Brazilian Society of Dengue and Arboviruses, estimates that as many as 90 percent of mosquito breeding grounds can be found in people’s homes. That means Saturday’s effort may help raise awareness where it matters most. Still, he said, the benefits probably will be minimal.

“Just the media impact is worth the trouble,” Pamplona said. “Unfortunately, it’s not an ongoing effort. People have to understand that we can’t allow mosquitoes in our homes. Until we internalize that, we’ll keep having epidemics.”

On the working-class east side of São Paulo, 100 troops were deployed to a sprawling shopping center. Inside, as one group of soldiers played in a jazz band, others handed out pamphlets and chatted with shoppers. One of their recommendations: to properly seal water tanks, the kind that could be seen on the roofs of cinder-block homes on a hill behind the mall.

Shoppers shook hands with the soldiers and accepted pamphlets with a smile. But they also relayed stories that indicated the limits of the campaign. Osvaldo Cordeiro Souza, 70, said he had seen many residents of his neighborhood ignore health officials’ instructions.

In a nation with a high crime rate, trust is an issue. Another shopper, André Luiz, 27, used to work for the São Paulo city government to inspect homes for mosquito breeding grounds. “They thought we were there to rob them,” he said, “or that it was some kind of scam.”

Read more:

Brazil reports explosion of dengue, a bad omen for spread of Zika virus

Brazil pushes back at Zika critics, finds new evidence of link to birth defect

What is Zika? And what are the risks as it spreads?

Today’s coverage from Post correspondents around the world