- It is spread by the Aedes aegypti mosquito, which also carries dengue fever and yellow fever
- It was first discovered in Africa in the 1940s but is now spreading in Latin America
- Scientists say there is growing evidence of a link to microcephaly, that leads to babies being born with small heads
- While Zika virus can lead to fever and a rash, most people show no symptoms, and there is no known cure
- The only way to fight Zika is to clear stagnant water where mosquitoes breed, and to protect against mosquito bites
The announcement by the Rio authorities comes amidst growing attention around the world over the large number of cases of Zika in the Americas.
Brazil has the largest-known outbreak of the virus which has been linked to a spike in birth defects in new-born babies whose mothers were bitten by the mosquito during pregnancy.
The US, Canada and EU health agencies have issued warnings saying pregnant women should avoid travelling to Brazil and other countries in the Americas which have registered cases of Zika. (BBC News, 2016)