CDC reports asymptomatic Zika transmission; FDA begins universal blood testing



Officials at the Centers for Disease Control and Prevention have confirmed a case of Zika virus infection in a nonpregnant Maryland woman who likely contracted the virus through sexual intercourse with her asymptomatic male partner.

“To date, only one other case has been reported in which a man without symptoms might have sexually transmitted Zika virus to his female partner,” Richard B. Brooks, MD, and his colleagues wrote Aug. 26 in the Morbidity and Mortality Weekly Report (doi:10.15585/mmwr.mm6534e2). “However, in that reported case, both the man and the woman had traveled to a country with ongoing Zika virus transmission where they were likely exposed to mosquitoes.”

In the current case, the couple had condomless vaginal sex 10 days and 14 days after his return from the Dominican Republic, along with oral sex on day 14. Two days after the last encounter, the woman began exhibiting symptoms of Zika virus infection, namely, a maculopapular rash and a fever. She sought medical care 3 days later (19 days after her partner returned to the United States). She had no other sexual partners during this time. Meanwhile, the male sex partner reported no symptoms of a Zika virus infection, other than simply being tired from his recent travel.

“The findings in this report indicate that it might be appropriate to consider persons who have condomless 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,” the researchers wrote.

©Tomasz Gierygowski/

Transmission of Zika virus through blood transfusions is also a growing concern, particularly if an asymptomatic individual donated blood.

On Aug. 26, the Food and Drug Administration announced recommendations to test all donated blood and blood components across the United States and its territories for the Zika virus, to mitigate the chances of transmitting the virus through transfusions. In February, the FDA first issued guidance recommending that only areas with active Zika virus transmission screen donated blood.

“As new scientific and epidemiological information regarding Zika virus has become available, it’s clear that additional precautionary measures are necessary,” Luciana Borio, MD, FDA’s acting chief scientist, said in a statement. “We are issuing revised guidance for immediate implementation in order to help maintain the safety of the U.S. blood supply.”

In a conference call with reporters, Peter Marks, MD, PhD, director of the FDA’s Center for Biologics Evaluation and Research, said that while there have not yet been any confirmed cases of such transmission, donors and health care workers must be vigilant. “Given the frequency of travel of individuals within the United States, there is the risk that people without symptoms who are infected with Zika virus could potentially donate blood and thereby transmit Zika virus,” he said.

The CDC also published new numbers on Guillain-Barré syndrome (GBS), which has been on the rise in countries affected by Zika virus.

Individuals who began exhibiting any neurologic symptoms between Jan. 1, 2016, and July 31, 2016, and were suspected of possible GBS total 56. Of those 56 patients, 34 (61%) were found to have evidence of either Zika or another related flavivirus. Ten (18%) of those 56 were confirmed to have Zika virus, and 1 patient who received treatment for GBS died of septic shock. Thirty (88%) of the 34 found to have evidence of flavivirus also reported having an acute illness of some kind before the onset of neurologic symptoms. The figures come from the GBS Passive Surveillance System (MMWR. 2016 Aug 26. doi:10.15585/mmwr.mm6534e1).

“Persons with signs or symptoms consistent with GBS should promptly seek medical attention,” the CDC urged. “Health care providers who evaluate patients with neurologic illnesses should consider GBS and report suspected cases to public health authorities. Residents of and travelers to Puerto Rico are advised to follow existing recommendations for prevention of Zika virus infection.”

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