Q24N (CNN) – Speaking in front of Congress last week, Centers for Disease Control and Prevention (CDC) director Dr. Tom Frieden was blunt.
“We are figuring out more about Zika literally every day,” he said. “But as hard as we work, there are still many things that we cannot know now, and cannot do now.”
With the current state of knowledge about Zika, health officials believe that a person is only contagious for as long as they are symptomatic. The problem is that only one out of five people with Zika will have any symptoms at all.
But, as in the case of microbiologist Brian Foy who obtained Zika in Africa and passed it to his wife, it would appear that he was contagious before the worst of his symptoms began. “First known sexual transmission of Zika virus in U.S. was eight years ago”.
And then there’s the issue of how long the virus will last in semen
Male testicles, along with the eyes, placenta and the fetus, are what is known as “immune privileged” sites, areas of the body that have special protection from an inflammatory immune response. Simply put, it means your antibodies aren’t allowed in to kill off invaders, an evolutionary way of protecting procreation.
“Immune privilege” affected survivors of the most recent Ebola outbreak.
One U.S. man discovered Ebola in his eye months after his blood was declared Ebola-free. And Ebola has been found in the semen of male survivors in Sierra Leone for up to nine months after it had disappeared from their blood, although the volume of the virus does appear to reduce over time.
Other than the Dallas case, scientists today know of two more cases where Zika virus has been found in semen. One was during a 2013 outbreak in French Polynesia, just as the virus began its explosive spread around the world. A Tahitian man had three separate episodes of Zika; after the third, his semen showed high levels of the virus, even though it was undetectable in his blood.
A second documented case in the United Kingdom in 2014 found high levels of the Zika virus in semen up to 62 days after the onset of the illness; in fact the viral load was stronger at that time than when the first samples were taken.