The potential for Zika to be spread sexually has just increased massively, as researchers have found that the virus can still be detected in the sperm of infected men up to six months after being diagnosed with the disease. This worrying development could see the recommendations from the World Health Organization and the Center for Disease Control change, as they come to terms with the ever-shifting evidence and how best to deal with it.

The longest the virus had been detected in semen previously was up to 93 days after diagnosis, or just over three months, whereas this latest report has almost doubled that period. It now raises the very real possibility that this virus can replicate itself in the genital tract of men, meaning that even without the mosquitos that normally spread the disease, Zika can still be passed on, although it is as yet unknown whether or not the virus detected in the sperm in this latest study can lead to infection.

The research is based on work carried out by doctors at the Spallanzani Institute of Infectious Diseases in Rome. They have been following an Italian man in his 40s who contracted Zika while on a two-week trip to Haiti in January this year. Since returning home and showing symptoms of the disease, he has been regularly tested for the virus. The doctors found that while it could be detected in his blood up to five days after infection, and urine up to two weeks after, it persisted in his saliva for 47 days and worryingly was still being detected in his semen 181 days later.

The results go to show how the Zika outbreak in the Americas is a continuously developing situation that needs constant monitoring. While much of the focus has been on the spread of the disease via mosquitos, there is a growing awareness that sexual transmission of the virus also needs vital attention. Currently, the guidelines state that men who have been diagnosed with Zika should practice safe sex for up to six months after detection, though in the light of this new evidence it is likely that those recommendations will now have to be revised.

With an estimated 1.5 million people already having been infected with Zika in the Americas, and the first cases of mosquitoes spreading the virus in the United States, there has been a huge push to develop an effective vaccine against the disease. There have been some tentative successes, and human trials for some have even been approved, but the likelihood that these will ready for the current outbreak is not particularly good.