Zika may be sexually transmissible for shorter period than previously thought
The period during which Zika virus can be sexually transmitted is shorter than was estimated in the earliest studies published after the epidemic, according to results of a living systematic review published in PLOS Medicine.
“Zika virus (ZIKV) can be transmitted between humans through sexual contact, although it is most commonly transmitted by infected Aedes spp. mosquitoes,” researchers in Switzerland and the United States wrote. “Sexual transmission of ZIKV has important implications for public health, for people living in endemic regions, and sexual partners of travelers returning to nonendemic regions from endemic regions because ZIKV infection during pregnancy can cause congenital infection of the fetus and because ZIKV infection can trigger the immune-mediated neurological condition Guillain-Barré syndrome.”
A CDC spokeswoman told Infectious Disease News in April that the agency would re-evaluate its guidance for the prevention of sexual transmission of Zika virus based on findings published in The New England Journal of Medicine that showed that men can sexually transmit the virus for only a short period of time — perhaps just a few weeks after they become ill. Asked for an update, the spokeswoman said she was not aware of any changes to the guidance.
For the current study, researchers conducted a systematic search of literature published through April 18, 2018, including databases PubMed, Embase, bioRxiv, arXiv, PeerJ and LILACS, reporting on sexual transmission of ZIKV and other arthropod-borne flaviviruses in humans and other animals. They searched for data on seven elements of ZIKV sexual transmission, including rectal and vaginal susceptibility to infection, incubation time following sexual transmission, interval between symptom onset in primary and secondary infected individuals, duration of infectiousness, reproduction number, transmission probability per sex act and transmission rate.
Of 1,227 studies identified, 128 publications were reviewed in the study, including 77 that presented data on humans. Thirty-six couples reported sexual transmission of ZIKV, with 34 being male-to-female transmission. Fifteen couples had a reported median serial symptom onset interval of 12 days, with a maximum of 44 days.
Data from two prospective cohorts showed ZIKV RNA was present in semen for a median duration of 34 days (95% CI, 28-41 days) and 35 days. The researchers reported that aggregated data about ZIKV RNA from 37 case reports suggested there was a median duration of detection of ZIKV of 40 days and a maximum duration of detection of 370 days in semen. Median duration of detection of ZIKV was 14 days and a maximum duration of 37 days in human vaginal fluid.
The researchers detected infectious virus in human semen for a median duration of 12 days and a maximum duration of 69 days.
They reported that there was low certainty in the reproduction number for sexual transmission of ZIKV. They also noted that evidence was lacking on sexual transmission of other flaviviruses.
“In humans, we estimated the serial interval for sexually transmitted infection to be 12 days,” the researchers wrote.
They added that the findings “suggest that the infectious period for sexual transmission of ZIKV is shorter than estimates from the earliest post-outbreak studies, which were based on [reverse transcription polymerase chain reaction] alone.” – by Bruce Thiel
Disclosure: Counotte reports no relevant financial disclosures. Please see the study for the other author’s relevant financial disclosures.