The U.S. Food and Drug Administration called Friday for all blood donations in the U.S. to be screened for Zika virus. The move deviates from the medical agency’s guidance released in February, which recommended screening only for areas with active transmission of the virus via the mosquito population. The new advisory applies to whole blood and blood components used in the U.S. and its territories.
“There is still much uncertainty regarding the nature and extent of Zika virus transmission,” Peter Marks, director of the FDA’s Center for Biologics Evaluation and Research, said in a statement. “At this time, the recommendation for testing the entire blood supply will help ensure that safe blood is available for all individuals who might need transfusion.”
The guidelines come as instances of non-travel-related infections appear outside of Miami. On Monday, Florida Gov. Rick Scott announced a locally transmitted case in Pinellas County near Tampa Bay, while Palm Beach County reported its second local infection on Wednesday. Further south, Miami-Dade County has experienced 39 local infections, while Broward noted one. Overall, the state has recorded 577 cases of the disease.
Elsewhere, a Maryland man without symptoms appears to have spread the virus to his partner via intercourse, according to a new report from the Centers for Disease Control and Prevention. The man in question traveled to the Dominican Republic, returned and had condomless sex with his partner, and she developed a Zika infection with symptoms 10 days later.
This is potentially the first reported case of a symptomless individual spreading the virus sexually. (France reported a possible incident in April, but in that case, both partners had recently traveled to a country with active Zika transmission.)
The CDC is careful to state that this single case doesn’t mean every asymptomatic person returning from a Zika-hit nation carries a risk of sexually transmitting the virus. But the case report raises new concerns about the reach of the virus.
Sexually transmitted cases of Zika represent a small minority of total infections — 22 of the 2,517 reported in the continental U.S. so far. Meanwhile, three out of every four people infected with Zika don’t display symptoms. That means the total scope of Zika transmissions caused by sexual intercourse with asymptomatic individuals is a mystery, especially in U.S. territories like Puerto Rico, where sexually transmitted cases cannot be tracked because they overlap so heavily with mosquito-borne transmission.
“Ongoing surveillance is needed to determine the risk for sexual transmission of Zika virus infection from asymptomatic persons,” the report states. “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.”
A second report released today by the CDC highlights Zika-related Guillain-Barre syndrome (GBS) cases in Puerto Rico. Though Zika is better known for causing microcephaly and other birth defects, the virus has also been linked to GBS, a rare autoimmune disorder in adults.
The Puerto Rico Department of Health with an assist from the CDC identified 56 suspected GBS cases between January 1 and July 31. Of these cases, 26 had a confirmed or presumed Zika infection based on screening. Laboratory tests tied another eight GBS cases to flavivirus infections, but couldn’t distinguish between Zika virus or the related dengue virus.
Overall, the number of GBS cases linked to Zika virus or an associated flavivirus is 2.5 times greater than those cases without ties to these mosquito borne-diseases. Plus, the GBS case count has increased each month since April, when the rainy season (and mosquito season) started. As of August 25, Puerto Rico has recorded 14,181 cases of Zika virus.