Brazil's armed forces mobilised 200,000 military personnel on a "day of action" to raise awareness of the Aedes aegypti mosquito that carries the Zika virus.
It is the first time the Army has deployed in force on home soil since the World Cup in 2014 when soldiers helped to secure Rio de Janeiro against gang violence.
The Zika epidemic is concentrated in the north-eastern state of Pernambuco, but the strategic battleground is in Rio.
A third of the troops were deployed in the city. Rio will host the Olympic Games in August, making it imperative for Brazil's Government to defeat the virus there.
"If there wasn't the Games, I don't think there would be so much worry," said Claudio Jorge Pessanha, 73, who was visited by Marines at his home near Maracana stadium, where the Olympic opening ceremony will take place.