How Long Does Zika Remain Infectious in Semen?

Zika virus ribonucleic acid (RNA) is commonly found in the semen of men with symptomatic Zika virus, especially within the first month after symptom onset, and can persist for up to 6 months, according to a new study. However, shedding of infectious Zika virus was limited to the first few weeks following onset.

During their study, researchers evaluated semen samples from 184 men and urine samples from 183 men that were obtained 14 to 304 days after the onset of the virus. Samples were collected twice monthly for 6 months after symptom onset.

Each sample was tested using real-time reverse-transcriptase-polymerase-chain-reaction (RT-PCR) assay and by Vero cell culture and plaque assay for for Zika virus RNA and infectious Zika virus, respectively.

Out of 1327 semen samples and 1038 urine samples that were collected, Zika virus RNA was present in the semen of 60 men (33%) and in the urine of 7 men (4%). Notably, Zika virus RNA was present in 22 of 36 men (61%) who were tested within 30 days after illness onset.

For most participants, Zika virus RNA shedding in semen declined significantly in the 3 months after illness onset, with the only exception being 1 man in whom viral shedding continued for 281 days.

Factors such as older age, less frequent ejaculation, and the presence of certain symptoms at the time of initial illness were found to predict prolonged RNA shedding.

“[Zika virus] RNA was commonly present in the semen of men with symptomatic [Zika virus] infection and persisted in some men for more than 6 months,” the researchers concluded. “In contrast, shedding of infectious [Zika virus] appeared to be much less common and was limited to the first few weeks after illness onset.”

—Christina Vogt

Reference:

Mead PS, Duggal NK, Hook SA, et al. Zika virus shedding in semen of symptomatic infected men [Published online April 12, 2018]. N Eng J Med. doi: 10.1056/NEJMoa1711038.