From the Journals

Zika virus: Sexual contact risk may be limited to short window

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Guidelines should change as data emerges

This study illustrates the apparent shortcomings of current virus-detection standards in terms of their relevance to public health, according to Heinz Feldmann, MD.

Approximately 4% of Zika virus RNA-positive semen samples were infectious, according to the report, and of those infectious samples, all were obtained within 30 days of the onset of illness. “This finding suggests that there is a short period during which Zika virus–infected men might transmit this virus through sexual contact,” Dr. Feldmann wrote in an editorial.

Current practice in some areas is to test semen samples sequentially until two or more consecutive negative results are obtained; however, that approach is controversial, according to Dr. Feldmann, because the person could be shedding the virus intermittently because of the potential for virus latency and reactivation.

“This also raises the question of whether modern molecular approaches are properly positioned to detect virus latency rather than persistence,” he said in his editorial. The goal, he added, should be to determine infectivity, which is probably best assessed by means of viral isolation – which is believed to be less sensitive than molecular detection.

“Thus, the diagnostic situation is far more complicated than it seems,” he noted.

However, he added, these diagnostic scenarios may be less applicable for public health entities, which have “quickly” disseminated recommendations for safer sex to prevent Zika virus spread and the potentially devastating consequences of fetal infection.

“These recommendations leverage the best data available and have been implemented, but ought to be updated as new data emerge,” Dr. Feldmann wrote.

Dr. Feldmann is with the National Institute of Allergy and Infectious Diseases, National Institutes of Health, and Rocky Mountain Laboratories, Hamilton, Mont. These comments are derived from his editorial N Engl J Med 2018;378:1377-85 . Dr. Feldmann reported that he had nothing to disclose related to the editorial.



Shedding of infectious Zika virus in the semen of symptomatic infected men appears to be uncommon and limited to the first few weeks after onset of illness, according to results of a recent prospective study.

Out of all semen samples with detectable Zika virus RNA, the only ones with infectious virus were those that had been obtained within 30 days of illness onset, study authors reported in the New England Journal of Medicine.

“The shedding of infectious Zika virus that could be cultured was rare, short-lived, and limited to the few samples with at least 7.0 log10 Zika virus RNA copies per milliliter of semen,” wrote first author Paul S. Mead, MD, MPH, of the National Center for Emerging and Zoonotic Infectious Diseases, Fort Collins, Colo., and his coauthors.

Sexual transmission of Zika virus, first documented in 2011, has now been reported in at least 13 countries, Dr. Mead and his colleagues wrote.

Usually, the cases have involved transmission from a symptomatic man to a woman, they added.

Previously, some investigators had proposed that sexual transmission of Zika virus could pose a greater risk of fetal infection than could mosquito-borne transmission, Dr. Mead and colleagues noted in their report. “If so, the interruption of sexual transmission could play a critical role in preventing the serious complications that have been associated with fetal infection,” they wrote.

To investigate further, Dr. Mead and his colleagues conducted a prospective study of men with symptomatic Zika virus infection. They collected 1,327 semen samples from 184 men and 1,038 urine samples from 183 men, according to the report.


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