Study Shows Zika Virus Persists in Body Fluids

Although most Zika virus (ZIKV) infections are transmitted by infected mosquitoes, ZIKV transmission has been documented as occurring through sexual contact, blood transfusion, laboratory exposure, and both intrauterine and intrapartum transmission.

ZIKV infection can be diagnosed through detection of ZIKV RNA in blood, urine, and other body fluids by reverse-transcriptase–polymerase-chain-reaction (RT-PCR) assays. However, the frequency with which ZIKV RNA can be detected in various body fluids and the length of time that it remains detectable are not well understood.


An international team of scientists cooperating with the Centers for Disease Control and Prevention (CDC, Atlanta, GA, USA) evaluated samples obtained from 295 participants (including 94 men who provided semen specimens) in whom ZIKV RNA was detected on RT-PCR assay in urine or blood at an enhanced arboviral clinical surveillance site. The study was based on 295 people in Puerto Rico infected with Zika beginning in May 2016. The team collected samples of serum, urine, saliva, semen, and vaginal secretions weekly for the first month and at 2, 4, and 6 months after diagnosis. The mean age of the participants was 36 years; 51% were female, including nine who were pregnant.

Specimens, measuring 200 μL, were tested by means of the Trioplex RT-PCR assay, as recommended by the CDC for the detection of dengue, chikungunya, and ZIKV RNA. In addition, they performed validation analyses for the use of the Trioplex RT-PCR assay in semen. Serum was tested by means of anti–ZIKV IgM antibody capture enzyme-linked immunosorbent assay. ZIKV isolation was attempted through culture in a subset of semen and serum specimens.

The investigators reported that the median and 95th percentile for the time until the loss of Zika RNA detection were 15 days, and 41 days respectively, in serum; 11 days, and 34 days in urine; and 42 days and 120 days in semen. Less than 5% of participants had detectable Zika RNA in saliva or vaginal secretions. Compared with preliminary findings, the median time of RNA clearance in semen rose from 34 to 42 days, and for 95th percentile it climbed from 81 to 120 days.

The authors concluded that the prolonged time until ZIKV RNA clearance in serum in this study may have implications for the diagnosis and prevention of ZIKV infection. In 95% of the men in this study, ZIKV RNA was cleared from semen after approximately four months.

Gabriela Paz-Bailey, MD, PhD, the lead author of the study, said, “Anyone concerned about getting or passing Zika through sex should use condoms every time they have sex or not have sex for at least three months after symptom onset to allow Zika virus to clear from semen. Because Zika infection during pregnancy can cause severe birth defects, pregnant women should not travel to areas with Zika transmission risk. All travelers should strictly follow steps to prevent mosquito bites and prevent sexual transmission during and after the trip.” The study was published on September 27, 2018, in The New England Journal of Medicine.

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