Zika Update: Female to Male Transmission and Risk at the Olympics

Although visitors to the Olympic Games are expected to have a “low probability” of mosquito-borne Zika infections because the Games will occur during the winter season in Rio de Janeiro, people should use common-sense strategies to avoid transmission while attending, including avoiding sexual transmission, according to an analysis from the Centers for Disease Control and Prevention (CDC).

The CDC issued several statements about Zika this week, including warning people about avoiding sexual transmission of Zika virus at the Games.1 This statement came one day before a statement noting that sexual transmission of the virus has occurred in New York, and was the first reported case of a woman transmitting the disease to her partner. 

The Olympics analysis notes that the Games were scheduled when the cooler and drier weather typically reduces mosquito populations. 

CDC officials conducted a risk analysis to predict those countries at risk for Zika virus importation exclusively attributable to the Games and noted that although there are an expected 350,000 to 500,000 international visitors and athletes expected to travel to Rio de Janeiro, Brazil for the Games, this travel volume represents a very small fraction – less than 0.25% – of the total estimated 2015 travel volume to Zika-affected countries.

CDC officials also noted that “whereas all countries are at risk for travel-associated exportation of Zika virus, CDC estimated Chad, Djibouti, Eritrea, and Yemen as having unique risk attributable to their travel for the Games.” The analysis notes that these countries do not have substantial travel to any country with local Zika virus transmission, except for their participation in the Games, and have environmental conditions and population susceptibility to sustain mosquito-borne transmission of Zika virus.

The analysis goes on to recommend prevention techniques for those who are traveling, including: 

  • “Pregnant women should not travel to the Games.
  • All visitors should take steps to prevent mosquito bites, both during travel and for 3 weeks after returning home.
  • All visitors to the Games should take measures to prevent sexual transmission.”

Sexual transmission is an important route of transmission, health officials said, noting that in New York City a report of female-to-male sexual transmission of Zika virus infection is the first documented case of sexual transmission of Zika from a woman to her sex partner.2 All previously reported cases of sexually transmitted Zika virus infection have been spread from men to their sex partners.

CDC officials recommend that all pregnant women who have a sex partner who has traveled to or resides in an area with Zika use barrier methods every time they have sex or they should not have sex during the pregnancy. Although no cases of woman-to-woman Zika transmission have been reported, these recommendations now also apply to female sex partners of pregnant women.

CDC is currently updating recommendations for sexually active people in which the couple is not pregnant or concerned about pregnancy and for people who want to reduce personal risk of Zika infection through sex.


  1. Grills A, Morrison S, Nelson B, et al.  Projected Zika Virus Importation and Subsequent Ongoing Transmission after Travel to the 2016 Olympic and Paralympic Games — Country-Specific Assessment, July 2016. MMWR Morb Mortal Wkly Rep. 2016; doi:10.15585/mmwr.mm6528e1.
  2. Davison A, Slavisnski S, Komoto K, et al.  Suspected Female-to-Male Sexual Transmission of Zika Virus — New York City, 2016. MMWR Morb Mortal Wkly Rep. 2016; doi: 10.15585/mmwr.mm6528e2.

This article originally appeared on Infectious Disease Advisor