New Zika cases call into question health officials’ guidelines on sexual activity

Two new reports call into question advice about how long men who have been infected with the Zika virus should wait before trying to father a child.

On Thursday, scientists described two cases in which the semen of men who contracted Zika in Haiti early this year continued to test positive for the virus, even though it has been six months since they were infected.

The semen of one tested positive 188 days after he first experienced symptoms of the illness. Testing on day 181 came back positive for the other man. Both men are still being followed. Previously, the longest period in which evidence of virus was seen in the semen of a Zika-infected man was 93 days.

The reports were published in the online journal Eurosurveillance, a publication of the European Center for Disease Prevention and Control.

The World Health Organization and the Centers for Disease Control and Prevention currently recommend that men who have had symptoms of Zika not attempt to father a child for six months after their illness. They also suggest that men who have been ill practice safe sex or abstinence if their partner is pregnant.

The CDC said it was aware of the new reports and is reviewing the issue to see if its guidance ought to be altered.

“We want to make the most informed recommendation as rapidly as possible based on full evaluation of the available science,” Dr. John T. Brooks, a senior medical adviser in the division of HIV/AIDS prevention, told STAT.