![](http://media.nzherald.co.nz/webcontent/infographics/913/BloodONLINE-ARTICLE-620X52.jpg)
Olympians returning directly from Rio will face a four-week blood-donation stand-down because of the city's being in the zone of mosquitoes that carry viruses.
The stand-down period may be even longer if the athletes went to rural areas. The mosquitoes carry dengue, Zika and chikungunya viruses.
Female athletes will be deferred for four weeks following sex with a man diagnosed with or suspected of having Zika within the preceding three months.
Eligibility to donate blood is affected by many factors, including illness, pregnancy, breastfeeding, age, travel and potential exposure to blood-borne infections.