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.



Infectious Zika virus was isolated from just 3 out of the 78 semen samples with detectable Zika virus RNA that were tested by culture, investigators said. Notably, all 3 of the cases were among the 19 of those samples obtained within 30 days of illness onset, they reported.

Detection of Zika virus RNA in urine was rare, occurring in only 7 men (4%), possibly because of the timing of the first specimen collection, according to investigators. They said previous studies suggest a rapid decline in Zika virus shedding in urine during the first few weeks after onset of illness.

Important questions remain regarding sexual transmission of Zika virus, such as whether maternal infection through sex poses similar risks to the fetus as compared with maternal infection via mosquito bite, Dr. Mead and his coauthors said in the report.

“A better understanding of these issues is needed to guide the development of effective prevention strategies,” they wrote.

The study was supported by the Centers for Disease Control and Prevention. Dr. Mead and his coauthors reported they had no disclosures related to the study.

SOURCE: Mead PS et al. N Engl J Med. 2018;378(15):1377-85.


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