N. Engl. J. Med. 378, 1377–1385 (2018)

Zika virus RNA is commonly shed in the semen of infected men, and in some of these men, this occurs beyond 6 months after the first appearance of symptoms. Shedding of infectious virus, however, appears to be limited to the month immediately after illness onset.

Zika virus is transmitted by mosquitoes and during recent outbreaks has been linked to the development of congenital microcephaly in the offspring of infected individuals. There have been reported cases of male-to-partner sexual transmission, but the duration of contagion is unknown.

Mead et al. analyzed levels of Zika virus RNA in semen samples from 184 symptomatic men (1,327 total samples) every 2 weeks over a period of 6 months. Zika virus RNA was commonly detected, and the duration of shedding was linked to ejaculatory frequency and joint pain. Detection of infectious virus in semen was less common and was rarely observed beyond the first few weeks of illness onset.

Interruption of sexual activity during the early symptomatic phase of Zika in men could be important in preventing transmission.