By Dennis Thompson
The researchers said Zika may only be present in semen for about a month. Previous research had suggested that Zika virus can be found in semen for as long as 188 days after the onset of symptoms.
The new study included 12 men in French Guiana who had Zika virus. Four of the men never had any detectable Zika in their semen. One excreted Zika virus in his semen for at least three days. And seven had Zika-laced semen for at least a month, the researchers reported. The maximum duration of detectable Zika in semen in the study was 45 days.
"These data suggest that not all men who are symptomatically infected with Zika virus will have Zika virus RNA detectable in semen," Dr. Franck de Laval, of the Military Center for Epidemiology and Public Health in Marseille, France, and colleagues wrote.
The results also showed that Zika does replicate in the testicles or semen-producing glands, since the amount of Zika in semen was significantly different than the Zika load found in the men's blood.
"More data are needed to better inform public health recommendations," the study authors suggested.
Zika virus is most often transmitted via mosquito bite. But the virus also can be sexually transmitted, according to the U.S. Centers for Disease Control and Prevention.
It's unlikely the CDC recommendations will change based on these findings, an infectious disease expert said.
Dr. Daniel Caplivski is director of the Travel Medicine Program and associate professor for the division of infectious diseases at the Icahn School of Medicine at Mount Sinai in New York City.
"Unfortunately, the fundamental recommendations of public health experts regarding delaying pregnancy after Zika virus infection or exposure are unlikely to change, given the degree of uncertainty that remains from other studies in which the genetic material of the virus was detectable for longer periods of time," Caplivski said.
And despite these findings, people should still follow the CDC's Zika guidelines for safe sex, health experts said.
According to Dr. Amesh Adalja, a senior associate with the Johns Hopkins Center for Health Security, in Baltimore, "Because it is unclear which men will have longer persistence, it is important for Zika-infected/exposed men to practice safe sexual practices for six months post-infection to avoid transmission of the virus."
Women's health specialist Dr. Jill Rabin said the small size of the study warrants a larger follow-up.
"The good news is it may last a shorter period in men than recorded previously, but we need to have a larger sample size and follow people for a longer period of time," Rabin said.
"Because we don't have enough data and we don't have enough people, we can't really say what is the time period needed to be free of infection," she added.
Zika causes neurological birth defects, most commonly microcephaly, a condition in which a baby's brain and skull are underdeveloped, Rabin said. She's co-chief of the division of ambulatory care with Women's Health Programs-PCAP Services at Northwell Health in New Hyde Park, N.Y.
There's also concern that Zika-exposed babies seemingly born healthy will develop learning disabilities or problems with hearing or sight later in life, Rabin noted.
"Women of reproductive age do not want to have a baby born with Zika," she said. "You want to follow the worst-case scenario, and the worst-case scenario is it could last up to six months. Why would you take a chance with your baby?"
The study was published as a letter in the Aug. 17 issue of the New England Journal of Medicine.