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Zika RNA persists longer in semen than other body fluids

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October 2, 2018

Gabriela Paz-Bailey, MD, PhD, MSc
Gabriela Paz-Bailey

Zika virus RNA duration was the longest in semen compared with other body fluids, according to study results published in The New England Journal of Medicine.

“Our study looks at how long Zika virus particles remain in blood serum, urine, semen and other body fluids,” Gabriela Paz-Bailey, MD, PhD, MSc, from the lead epidemiology team at the CDC’s Dengue Branch, told Infectious Disease News. “We found that half of participants had detectable Zika virus particles in their blood at 15 days and in their urine at 11 days. Duration was the longest in semen. In a few men, parts of the virus were detected in semen for as long as 4 months.

“Importantly, presence of Zika virus particles in a person does not necessarily indicate that the person can transmit the virus to others,” she added. “The maximum time after symptom onset that we were able to isolate infectious Zika virus was 38 days.”

Preliminary results of the report had been originally presented at the 2017 Conference on Retroviruses and Opportunistic Infections.

Bailey and colleagues studied samples from 295 participants (mean age, 36.3 years; 51.2% female) in Puerto Rico who were recently infected with Zika virus (ZIKV) to estimate the frequency and duration of detectable ZIKV RNA in body fluids. Participants included nine pregnant women.

The researchers used reverse-transcriptase PCR (RT-PCR) assay in urine or blood at an enhanced arboviral clinical site to detect ZIKV RNA. They collected samples of serum, urine, saliva, semen and vaginal secretion weekly for the first month and at 2-, 4- and 6-month time periods. Ninety-four men provided semen samples.

Participants with ZIKV RNA detected in any specimen type at week 4 continued body fluid collections every 2 weeks until all specimens tested negative.

The time until ZIKV RNA could no longer be detected in serum was 15 days (95% CI, 14-17 days) for the median percentile and 41 days for the 95th percentile (95% CI, 37-44 days), compared with 11 days (95% CI, 9-12 days) and 34 days (95% CI, 30-38 days) in urine, respectively. The time until ZIKV RNA was no longer detectable was much higher in semen, with 42 days (95% CI, 35-50 days) for the median percentile and 120 days for the 95th percentile (95% CI, 100-139 days). Saliva or vaginal secretions contained detectable ZIKV RNA in less than 5% of participants.

Paz-Bailey told Infectious Disease News that the study results have influenced the CDC’s guidance on avoiding sexual transmission of ZIKV.

“CDC updated its sexual transmission prevention recommendations in August 2018, and our study was part of the evidence used to update the recommendations,” she said.

The CDC now recommends that couples in which the man was exposed to Zika should use condoms or not have sex for at least 3 months after possible Zika exposure. Women with possible Zika virus exposure should wait at least 2 months from beginning of symptoms or most recent exposure before trying to become pregnant.

Paz-Bailey said the study data on the isolation of infectious virus in semen support these recommendations.

“We used two methods to look for Zika virus in semen,” she said. “We found that detection of Zika virus genetic material decreased substantially during the first 3 months after illness but, at 4 months, still 5% had virus particles present. In contrast, detection of infectious Zika virus particles was rare and limited to a few samples collected within 38 days after illness. Finding viral RNA does not necessarily mean the virus that can cause an infection is present or that a person can spread it to others. Anyone concerned about getting or passing Zika through sex should use condoms every time they have sex, or not have sex for at least 3 months after symptom onset to allow Zika virus to clear from semen.”

The researchers also wrote that “the observed duration of ZIKV RNA in serum was longer than detection times reported for dengue virus. More than 90% of the patients who are infected with any of the four dengue viruses clear RNA within 10 days after the onset of symptoms.”

“Understanding how often and for how long evidence of Zika virus can be found in different body fluids can improve testing methods and could have implications for prevention and education efforts,” Paz-Bailey said. – by Bruce Thiel

Disclosures: Paz-Bailey reports no relevant financial disclosures. Please see the full study for other authors’ relevant financial disclosures.