Silent Transmission of Zika Virus Breeds New Challenges

With new cases of the Zika virus emerging by the day in Florida, residents of much of the southern half of the United States are already on edge.

Now, news has emerged of a case in Maryland involving the identification of Zika infection in a woman who had sexual contact with a man who did not know he was sick because he was asymptomatic. Upon investigation, it was determined that the man in question had, in fact, traveled to a Zika-affected area (the Dominican Republic) and had been exposed to mosquitoes while there.

However, although he sustained bites, “he reported that he had no symptoms consistent with Zika virus infection (i.e., fever, rash, conjunctivitis, or arthralgias) either during his travel or since his return, and he did not have any of the following other symptoms: myalgias, chills, eye pain, oral ulcers, genital ulcers, anal ulcers, hematospermia, hematuria, dysuria, and prostate pain.” The revelation, published in the August 26 issue of the Centers for Disease Control and Prevention’s (CDC) Morbidity and Mortality Weekly Report (MMWR), has called into question the current understanding of the virus and whether current surveillance protocols are adequate for the identification of new cases.

In the MMWR article, written by Richard B. Brooks, MD, of the Prevention and Health Promotion Administration in the Maryland Department of Health and Mental Hygiene (DHMH), and colleagues note that the woman in the case, who was not pregnant, presented to her healthcare provider in June 2016 with “a subjective fever and an itchy rash.” Laboratory testing at the Maryland DHMH confirmed Zika virus infection. The woman had not traveled to a region with ongoing transmission of Zika virus.

However, she and her male partner “reported having had condom-less vaginal intercourse twice after the man’s return from the Dominican Republic and before the woman’s symptom onset, approximately 10 days (day 10) and 14 days (day 14) after the man’s return.”

In addition, the man reported that he received fellatio from the woman during their sexual encounter on day 14. And, on day 16, the woman developed symptoms of Zika. She sought treatment 3 days later. Maryland DHMH performed Zika virus rRT-PCR testing, which was negative on serum and plasma and “equivocal on urine.” Serologic testing was positive for Zika virus IgM antibodies using the CDC Zika MAC-ELISA and positive for Dengue virus IgM antibodies using a commercial ELISA kit.

This is only the second case of an asymptomatic male passing the virus on to his female partner via sexual contact; however, in the first case, both the male and female had traveled to a country with ongoing Zika transmission. Dr. Brooks and his colleagues conclude that “ongoing surveillance is needed to determine the risk for sexual transmission of Zika virus infection from asymptomatic persons. The findings in this report indicate that it might be appropriate to consider persons who have condom-less sex with partners returning from areas with ongoing Zika virus transmission as exposed to Zika virus, regardless of whether the returning traveler reports symptoms of Zika virus infection.”

“Providers should request Zika virus testing for any patients with illness compatible with Zika virus disease who have had sexual exposure without barrier devices to prevent infections to a partner who traveled to an area with active Zika virus transmission,” they continue. “Such patients should also be reported to local or state health departments.”

At present, CDC recommendations for the prevention of sexual transmission of Zika virus in travelers returning from regions with active transmission differ depending on whether the traveler is symptomatic and, if it involves a couple, whether or not they plan to become pregnant.

Brian P. Dunleavy is a medical writer and editor based in New York. His work has appeared in numerous healthcare-related publications. He is the former editor of Infectious Disease Special Edition.