The grim story of the Zika epidemic took a minor detour yesterday with a report from Dallas that a case of sexually transmitted infection had been identified.
Though the CDC and the Dallas health authorities are not saying much, we were informed that a person who returned from Venezuela—where the virus is circulating—had sex with a local Texan and now the Texan has Zika infection. According to report, neither partner is pregnant.
It is altogether unsurprising to hear of case of sexually transmitted Zika or Ebola, or any virus that enters the bloodstream. There previously has been an almost-certain case of sexually transmitted Zika in the U.S.: In 2008 a man working in Senegal, where Zika was in the community, went home to Colorado. There, he developed symptoms of an inflamed prostate as well as bloody sperm (hematospermia); he also had sex with his wife. She became infected with Zika while their four children did not, suggesting it was spread from sex, not close physical contact. For those looking for a lurid read, turn elsewhere; in this cautious medical article, sexual spread is referred to as “non-vector-borne transmission.”
A few years ago in France, a person seeking treatment for bloody sperm was found to have Zika in sperm and urine, though the man was not known to have transmitted the infection.
Although slightly important, the Dallas story is more flash than substance, at least right now. There is reason to think that the urge to copulate might be depressed by active Zika infection, given the uncomfortable rash, severe joint aches, headache, and fever that occur 5-10 days after infection. In contrast, for HIV, the time from infection to symptoms is profoundly different: Once infected with HIV, a person is free of symptoms but contagious for 5 to 10 years, making transmission much more likely.
The contribution to the Zika epidemic of sexual transmission will be determined by two variables: first, the proportion of infected (and contagious) persons who never have symptoms, which is now tagged at about 80 percent.
Second—and more important—will be establishing the duration of time an infected man has virus in blood and sperm. If the virus mostly disappears after symptoms abate, then sexual transmission will be unusual. If however the virus sticks around for weeks and months, as happens with Ebola and other viruses, a secondary—and tertiary—wave of infection may be seen from sexual partners of patients.
In this regard, I suspect a recommendation will be given to use condoms for several months after infection, similar to the advice given post-recovery from Ebola. Zika, hopefully, will scare people into using condoms more frequently; fear is a wonderful motivator and any reason to use a condom is good for maintenance of public health.
The Dallas case surely adds some literal sexiness to the frightening epidemic and, of course, anyone who witnessed the AIDS epidemic is aware that a sexually transmitted virus can cause a public health calamity.
But right now and for a long while, it is crucial to remember that mosquitos are the problem, not people who have unprotected sex with travelers returning from endemic areas. Any distraction from this core truth, which admittedly lacks flash and sexiness, will serve only to prolong the Zika epidemic.