Can Zika be sexually transmitted? A recent report from Dallas says yes. And a few case studies says it has occurred in the past. But what does this really mean in terms of predicting this mode of transmission in the future, much less getting people worried? Not much.
Assuming that the Centers for Disease Control and Prevention (CDC) report about the Dallas case is correct (likely), this needs to be kept in perspective. It is one case and viruses that are far more prevalent and well-studied tell us that one case means very little.
Two of the most prevalent blood-borne viral infections in the world today are HIV and hepatitis C. These can give us some insight into Zika. With a huge caveat.
While it has been clearly established since 1982 that HIV is sexually transmitted, transmission of hepatitis C (HCV), which is four-times more prevalent than HCV, occurs primarily by blood, not sex. But even this remains controversial. Although sexual intercourse is considered to be a low risk factor in transmission of HCV, it is not zero. Leading health agencies can't be sure, but it is clear that sexual transmission of HIV is far more common.
So where might that leave Zika, another blood-borne infection, which belongs to the same family of viruses as HCV? The question that needs to be answered is whether Zika behaves more like HIV, or like HCV.
This may be difficult to establish, since HCV was first discovered in 1989, there have 170 million cases, but there is still no firm consensus about the importance of sexual transmission. So, one case of Zika tells us very little.
And that is after 27 years. For these reasons, there is unlikely to be an answer to the Zika question anytime soon, but experts at American Council on Science and Health are standing by to answer detailed questions.