In the summer of 2008, an American researcher developed symptoms of fevers, chills, fatigue and a maculopapular rash on his torso 1 week after returning from Senegal where he had been working on a mosquito sampling project. Around the same time his wife, who had not travelled outside of the United States, developed similar symptoms. Further testing revealed that the couple had contracted Zika virus (ZIKV). This was one of the first documented cases of sexual transmission of ZIKV.
Given this presence of ZIKV in semen and the congenital birth defects associated with ZIKV infection during pregnancy, the CDC recommended that men traveling from a Zika endemic area use condoms or refrain from or refrain from having sex for 6 months. The recommendation for women travelling from a Zika endemic area was to wait at least 8 weeks before attempting to conceive.
In April of this year, Mead and colleagues published the results of a study of viral shedding of ZIKV in semen of men who tested positive for ZIKV. In this study, infectivity of ZIKV was limited to the first 30 days after symptom onset. In this week's issue of NEJM, Paz-Bailey and colleagues report the presence and duration of detectable ZIKV in various body fluids in ZIKA RNA-positive individuals. The ZIKA Persistence (ZiPer) study prospectively followed 295 symptomatic individuals who tested positive for ZIKV at participating sites in Puerto Rico from 2016 to 2017. Serum, urine, saliva, semen, and vaginal swabs were collected weekly for the first month and then at 2, 4, and 6 months. The authors estimated the median and 95th percentile for the time until the samples tested negative.
In this study, ZIKV RNA was more frequently detected in urine than serum, and was infrequently detected in saliva and vaginal secretions (<5%). In serum, the median time to loss of ZIKV RNA detection was 15 days and the 95th percentile was 41 days. In urine, the median time to clearance of ZIKV RNA was 11 days and the 95th percentile was 34 days. In semen, the median time to clearance of ZIKV RNA was 42 days and the 95th percentile was 120 days.
Preliminary results of this study were published last year online in NEJM, and based on these preliminary data, the CDC updated their sexual transmission guidelines and shortened duration for use of condoms or abstinence in men with possible ZIKA exposure from 6 months to 3 months. Given the frequency of ZIKV RNA detection in different body fluids varies across studies and the variability in the frequency of ZIKV RNA detection in this study, better methods to evaluate for ZIKV are needed.
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Amanda Fernandes is a 2018-2019 NEJM editorial fellow.