Brazil is experiencing an outbreak of the Zika virus, which is spreading rapidly through Latin America and has been linked to birth defects. Pregnant women have been urged to avoid travel to affected areas.
Rio organizers have tried to calm fears that the Olympics may be affected, saying there is only a risk to pregnant women and the games will not be canceled. The games will also be held in Brazil's winter, when colder temperatures should reduce the mosquito population.
The International Olympic Committee has expressed confidence in measures being taken against the virus in Brazil and is following the advice of the World Health Organisation.
The mosquitoes that spread the Zika virus are among the hardest species to fight because they live and breed in spots where water collects inside houses and yards. However, the insect is not the only cause of infection. The Zika virus is now known to have been transmitted through saliva, blood and urine.
Should the Olympics be called off? Here is the latest selection of Your Views: