Scientific evidence of sexual transmission of the Zika virus

Well, we know now that ZIKA causes microcephaly, at least that is the latest findings. Things don’t look so good on other ZIKA fronts either, a new study confirms that the virus can be transmitted sexually. The analyses have shown 100% genetic correlation between the form of the virus present in a man who contracted the virus in Brazil and that of a woman who had never travelled in the epidemic area, but who had sexual relations with him.

For those of you interested, the ZIKA virus, a member of the Flavivirus family, is almost exclusively transmitted to humans by Aedes mosquitoes. No one really thought much of the Zika infection because it usually causes mild symptoms. Although as mentioned prior, it can be responsible for severe neurological complications for the developing foetus of a woman infected while pregnant. Some indications of possible sexual transmission of the virus have been reported, but scientists were not able to confirm that the virus could be transmitted sexually.

That is unfortunately no longer the case, for the first time, French researchers have been able to culture the infecting virus from two people seeking a consultation for suspected ZIKA infection. Specimens of urine, saliva and blood were taken from a man who returned from Brazil and had contracted the virus there. The same specimens were taken from a sick woman who had sexual relations with this man, but who had never travelled to an epidemic area.

I’m sure you are wondering how it was determined to be sexually transmitted and not from saliva or possibly even blood. However, while the virus was detected in the urine and saliva of the woman, analysis of the specimens showed that it was absent from the blood and saliva of the man, making it unlikely that transmission occurred by these routes. Furthermore, the researchers tested his semen for the virus and detected high viral loads at 15 days and at 3 weeks after the patient’s return from Brazil (approximately 300 million copies/ml).

To take it even further, the virus from both persons was individually sequenced (using a saliva sample from the woman and a semen sample from the man) for genetic analysis. Examination showed 100% correlation between the two genetic sequences. Apart from 4 mutations, all of them “synonymous,” the nucleotide sequences both encoded an identical form of the virus.

“Our work confirms, using molecular analyses, that sexual transmission of the ZIKA virus exists, and should be taken into consideration when making recommendations, due to its persistence in the semen several weeks after infection.”

“The period for which men should systematically have protected sexual relations (even oral) needs to be defined,” explains Yazdan Yazdanpanah.

This is probably the last nail in the coffin for the ZIKA virus mysteries as it were. There doesn’t need to be widespread panic quite yet; while the outbreak area seems to be spreading,cases of microcephaly are still a rather low occurrence. Not reassuring for the families suffering, but things could always be worse.

Sources:
D’Ortenzio, E., Matheron, S., de Lamballerie, X., Hubert, B., Piorkowski, G., Maquart, M., Descamps, D., Damond, F., Yazdanpanah, Y., & Leparc-Goffart, I. (2016). Evidence of Sexual Transmission of Zika Virus New England Journal of Medicine DOI: 10.1056/NEJMc1604449