Two cases suggest Zika could be spread via sex

A worker fumigating the Sambadrome ahead of the Rio Carnival in Brazil on Jan 26.
A worker fumigating the Sambadrome ahead of the Rio Carnival in Brazil on Jan 26. PHOTO: BLOOMBERG

NEW YORK • The Zika virus has already been linked to brain damage in babies and paralysis in adults. Now, scientists are facing another ominous possibility: That on rare occasions, the virus might be transmitted through sex.

The evidence is very slim; only a couple of cases have been described in medical literature. But a few experts feel the prospect is disturbing enough that federal health officials should inform all travellers, not just pregnant women, of the potential danger.

Officials at the Centres for Disease Control and Prevention, however, say the evidence is insufficient to warrant such a warning. While the two instances suggest a "theoretical risk" of sexual transmission, they note that the primary vector is clearly mosquitoes.


Dr Marcio Nehab, a paediatrician and infectious disease specialist at Fiocruz, a research institute in Rio de Janeiro, said that much more research was needed to definitively prove that Zika can be transmitted during sex.

"At the moment, we need to be more concerned with the mosquito, the vector known for transmitting the virus," Dr Nehab said in a bulletin about Zika geared towards women and children.

At the moment, experts know of just one case in the medical literature of live Zika virus being detected in a man's semen. The man was an unidentified 44-year-old Tahitian, exposed during an outbreak of the virus in French Polynesia in 2013. French scientists helping to investigate found high levels of the virus in semen samples taken from the patient, even after it disappeared from his blood.

It was unclear how long the virus had persisted in his body: He had had two episodes of fever that might have been caused by the Zika virus, one shortly before he was tested and another about two months earlier. The virus was also found in his urine.

Dr William Schaffner, chief of preventive medicine at Vanderbilt University Medical School, said it was imperative that research on possible sexual transmission of Zika be done in Brazil or another Latin American country experiencing an outbreak.

On Monday, the Pan American Health Organisation warned that Zika is likely to spread to every country in the Americas except Canada and Chile.

There is no vaccine or treatment for Zika. But GlaxoSmithKline is concluding feasibility studies evaluating whether its vaccine technology is suitable for the virus.

"We're concluding our feasibility studies as quickly as we can to see if our vaccine technology platforms might be suitable for working on Zika," Glaxo spokesman Anna Padula said in an e-mail. She added that vaccine development typically takes 10 to 15 years.


A version of this article appeared in the print edition of The Straits Times on January 27, 2016, with the headline 'Two cases suggest Zika could be spread via sex'. Print Edition | Subscribe