ZIKA virus infection is the only vector-borne disease — which is an ailment transmitted by mosquitoes — that has been found to also be transmissible through sexual intercourse.

Up until now, the only reported cases of sexual transmission in humans involved men who passed the Zika virus to women during sex via their ejaculation or semen.

Research also revealed the Zika virus to be present in men’s semen long after it has disappeared from their bloodstream. We should note that when we are first infected with Zika, the virus multiplies and can be found in our body fluids, including our blood and urine, until our body’s immune system is able to destroy and eliminate the virus.

FEMALE-TO-MALE TRANSMISSION

Now, the first case of a woman passing the Zika virus on to a man during sex has been reported in the Morbidity and Mortality Weekly Report of the Centers for Disease Control and Prevention (CDC) in the United States of America.

A non-pregnant woman in her 20s was reported to have had vaginal intercourse with a male partner without the use of a condom the day she returned from a country that has ongoing Zika transmission. She began experiencing symptoms of Zika one day after, including fever, fatigue, a maculopapular rash, swelling of her extremities, and heavier than usual menstruation.

On day three she visited her family doctor who collected urine and blood specimens that were sent to the lab for testing. Zika RNA was detected in both her blood (serum) and urine samples.

On day six the woman’s partner began experiencing symptoms of Zika and sought medical care. Testing revealed the Zika virus RNA in his urine sample, but not in his blood serum.

The CDC confirmed the results for both urine and blood samples from the couple, and interviews with the man appeared to rule out other possible causes for his infection. He said he had not travelled outside the USA in the preceding 12 months, nor had a mosquito bitten him within the week before the onset of his symptoms. Further, it was rare to have mosquitoes in his New York neighbourhood during the cold season.

The man had also reportedly not engaged in sex with anyone else recently, and his sexual encounter with the Zika-infected woman did not include oral or anal intercourse.

Thus, the article stated that the Zika virus in the woman’s vaginal fluids or menstrual blood may have spread to the man during exposure to his urethral passage or through undetected abrasions on his penis.

Earlier research elsewhere had found the Zika virus to be present in the genital tracts of females and in their vaginal fluid in particular.

PRECAUTIONS NECESSARY

As a result of this, the CDC in the USA has issued additional advice on how to avoid getting the Zika virus through sex.

All pregnant women should use barrier methods such as condoms during sex or abstain from sex if they have a partner who resides in an area that has active Zika transmission or has travelled to such an area.

Further, in light of the newly reported New York City case of transmission, the CDC is now extending these recommendations to both male and female sex partners of pregnant women, even though no case of woman-to-woman Zika transmission has yet been reported.

The CDC is also updating its recommendations for sexually active couples who are not pregnant, or who are concerned about pregnancy, as well as people who simply want to reduce their personal risk of Zika infection through sex.

It is strongly believed that the Zika virus can cause serious birth defects, most notably microcephaly that is characterised by unusually small head size and possibly severe developmental problems in young children. However, some sceptics are not convinced that the microcephaly seen in the cases in north-eastern Brazil are due solely to Zika virus infection, and believe other environmental issues contributed to the relatively large number of cases seen in that part of the country.

MORE RESEARCH NECESSARY

A lot of research on the Zika virus and its effects is currently occurring, and more is needed to determine specifically how the virus sheds in the genital tract and vaginal fluids, as well as the risk for transmitting the virus from a woman to a sexual partner.

More research is also necessary to explain why north-eastern Brazil experienced such a relatively high number of cases of microcephaly when compared to other Latin American countries like Colombia and El Salvador, that have not experienced similar proportional numbers of microcephaly in their Zika-infected population.

For us in the Caribbean, due to insufficient resources to conduct similar extensive research, we have to rely on the research findings obtained in other jurisdictions to help guide us in the advice we give to our population and the policies we make.

Therefore, we all must pay close attention to regular updates on this and related matters.

Derrick Aarons MD, PhD is a consultant bioethicist/family physician, a specialist in ethical issues in medicine, the life sciences and research, and is the ethicist at the Caribbean Public Health Agency – CARPHA. (The views expressed here are not written on behalf of CARPHA)