Mosquito Transmission not the only means

As much as most research has centered on Zika virus being a mosquito-borne disease, sexual transmission also plays a significant role in the spread. Weeks as well as months down the line after treatment, the virus can still be located in semen, making sexual contact a major transmission method. Also, expectant mothers can pass it on to the unborn babies.

Raising the Alarm

The CDC earlier this year confirmed that apart from Aedes aegypti mosquitoes harboring parasitic Zika virus being the primary transmitters, sexual contact has to be considered. That basically raised the alarm with recommendation that women should not only refrain from visiting the red zones but also keep off from sexual contact with people from these areas. A period of 6 months is recommended.

Shresta, an associate professor in LJI's Center for Infectious Disease, says that at the moment, most researchers tend to concentrate on prevention of Zika by focusing on mosquito control. But their “new work begs clinicians to also address whether sexual transmission of the virus constitutes a small or large proportion of cases."

Studying Zika Virus transmission pattern

In order to study how Zika virus is being transmitted, Sujan Shresta, Ph.D an investigator from La Jolla Institute for Allergy & Immunology (LJI) uses two different mouse models. The study involves placing Zika virus directly in the reproductive duct, which then replicates and goes into the bloodstream.

The investigators of Zika Virus transmission were aware that semen harbors the virus and can be easily transmitted vaginally, based on the rodent models. But some questions remained unanswered. These include what cells are infected and the stability of the virus in body fluids.

Their study involved injecting the experimental rodents with hormones so that two groups could be created, separated by the stages they are in terms of menstrual cycle. Post-infection, the results were striking. Those infected during their menstrual flow became weak, lost weight and eventually died after 2 to 3 weeks. The other group had no such signs, same day std testing.

The study lead author, William Weihao Tang, said that "The strain of mice we used - called AG129 - were originally engineered to be extremely vulnerable to infection. But even these mice, when infected in estrus phase, they appeared completely resistant to virus. That surprised us."

This trend was reflected in other experimental outcomes. For example, in both lethal and non-lethal strains, viral RNA, which serves as direct evidence of virus, persisted in the vaginal canal sometimes as long as 10 days post-infection in diestrus. By contrast, viral RNA disappeared three days after infection in estrus phase.

Thus, the researchers concluded that sexual transmission is bigger in human beings than originally thought. Considering that Zika virus can survive in male’s semen for several months without symptoms showing, one could possibly transmit to his sexual partner unknowingly. 

Contributor: admin