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CDC Releases New Zika Virus Guidance as New Sexual Transmission Information Emerges

The Centers for Disease Control and Prevention (CDC) has updated its interim guidance for “pre-pregnancy counseling” for Zika virus, just as new information regarding sexual transmission of the infection has been made available.
Among other provisions, the revised CDC guidance suggests that men with possible Zika exposure but no virus symptoms wait at least 6 months after their last possible exposure before “attempting pregnancy with their partner.” It is also recommended that these men use condoms during this time to prevent sexual transmission of the virus. In a statement released with the guidance update, the CDC said it based its new recommendations on its “ongoing assessment of available data.”
Some of that data likely appears in a series of studies published in the October issue of The Lancet Infectious Diseases, much of which is devoted to Zika virus-related research. In fact, a model for reducing the risk for an outbreak of sexually transmitted Zika virus proposed by researchers from the London School of Hygiene and Tropical Medicine, essentially supports the CDC’s 6-month “window,” noting that earlier studies have found the presence of viral RNA in the semen of infected males for up to 93 days after symptom onset.
Another paper published in the same issue of The Lancet Infectious Diseases suggests that Zika virus RNA may be present in semen and spermatozoa even longer than previously thought. In a case of travel-related Zika monitored by physicians in France, viral RNA was present in multiple collected semen samples 141 days after initial exposure. In two earlier cases investigated by the authors, viral RNA was still detectable in semen 69 days and 115 days, respectively, after symptom onset; in three other cases, however, viral RNA was undetectable after 20 days.

“The viral persistence in semen is of major concern and could be related to a viral tropism for male sexual cells,” the authors write.
In a commentary published in the same issue, authors from the CDC suggest that future assessments of sexual transmission of Zika virus should take lessons from the Ebola outbreak of 2014. They write, “Is the virus associated with spermatozoids or present in the seminal plasma? Is the virus harbored in the testes, a well-known immune-privileged site, or in the prostate? If the virus replicates and persists in the seminiferous tubules, what is the impact on semen quality (eg, morphology, count, mobility)? Answers to these questions could improve diagnostic testing for Ebola virus in semen, elucidate risk factors for viral persistence, and lead to better understanding of possible reproductive sequela of infection. Unfortunately, at the end of the west Africa Ebola virus disease outbreak, these questions remain largely unanswered. These questions are also unanswered for Zika virus.” They go on to suggest that studies designed to address these issues with Zika virus should be conducted “urgently and concurrently” with other disease response activities.

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