Zika Update: CDC Advice for Preventing Sexual Transmission

Areas with active Zika virus transmission in the Americas (CDC)

Guidance for preventing the sexual transmission of Zika virus was published in the Morbidity and Mortality Weekly Report on February 5th.

This article alludes to the three known cases of sexual transmission of Zika virus infection. These all involved male to female transmission with Zika virus being found in semen. In all cases the men were symptomatic.

The CDC is currently recommending abstinence or condom use for men with pregnant partners who are in or who have returned from areas where Zika virus transmission is occurring. In the above document the duration of time abstinence or condom use is recommended is not delineated. Some experts estimate up to 50% of pregnancies are unplanned, however. Given this, careful family planning consideration is warranted for all women with male partners residing in or traveling from areas with Zika transmission.

What is not known:

1) How long Zika virus can persist in semen after active infection. In one of the above cases it appeared to be present 2 to possibly 10 weeks following symptom outset; this is much longer than the virus is typically detected in the blood (less than or up to about a week).

2) How common is sexual transmission of Zika virus infection?

3) Will all men capable of sexually transmitting Zika virus be symptomatic?

4) Does female to male sexual transmission of Zika virus occur? What about male to male transmission? Or female

to female transmission?

5) How long should men who are in or who have returned from areas with Zika virus infection abstain from sex or use condoms?

At this point sexual transmission of Zika virus infection appears to be rare (with only 3 documented instances of this to date). More data is needed to answer the questions above and to best identify how to protect people living in and traveling to areas with Zika virus transmission.