Among the many concerns hanging over the Rio Games is that Brazil is ground zero for the mosquito-borne Zika epidemic, which has infected millions of people and caused the severe birth defect microcephaly in at least 2,000 babies. Fear of contagion, which can also come through sexual contact, has prompted several high-profile athletes to drop out and discouraged fans. Pregnant women, especially, have been advised to steer clear.
While the risk is real, health authorities say the likelihood of widespread Zika infections at the Olympics is low. A July study published in the journal Annals of Internal Medicine estimated between six and 80 new cases of the virus among travelers during the Games. One reason: August is winter in Brazil, when there are fewer mosquitoes out. Olympic venues will also practice mosquito-control measures like removing stagnant water. Experts offer another, bleaker reason for visitors to rest (somewhat) assured: those infected develop immunity, and Brazil already has an estimated 1.5 million cases, potentially slowing the pace of transmission.
This appears in the August 08, 2016 issue of TIME.