FDA Recommends Screening All US Blood Donations for Zika

All donated whole blood and blood components in the US should either be screened for the presence of Zika virus RNA or “pathogen reduced” to inactivate it, according to revised FDA guidance released in late August. The measures are intended to prevent Zika transmission via blood transfusion and “to keep our blood supply safe,” according to Peter Marks, MD, PhD, director of the FDA’s Center for Biologics Evaluation and Research. The new recommendations apply to every blood center in the US and its territories, not just to those in areas with active mosquito-borne transmission of Zika—currently Florida and Puerto Rico.

The new measures reflect both the severity of the Zika threat and the “tremendous uncertainty” about how long it is likely to persist, said Marks, who spoke with members of the press during a conference call announcing the revised recommendations. Issued on August 26, 2016, “Guidance for Industry: Revised Recommendations for Reducing the Risk of Zika Virus Transmission by Blood and Blood Components” supersedes previous FDA guidance on Zika, released in February and March of 2016.

Marks confirmed that 2 investigational tests for Zika are available for use under investigational new drug applications (INDs). Manufactured by Hologic, Inc and Roche Molecular Systems Inc, the individual-donor nucleic acid tests detect Zika virus RNA in blood. In contrast, pathogen-reduction systems inactivate viruses, bacteria, and parasites in blood products, reducing the risk of transfusion-transmitted infection. The first US-approved pathogen-reduction system, Cerus Corporation’s Intercept Blood System for platelets and plasma, received initial FDA approval in December 2014; 28 US blood centers currently use Intercept, according to the Cerus website. The company is also developing a pathogen-reduction system for red blood cells.

The FDA’s revised guidance pertains only to donated blood and the risk for transfusion-associated Zika transmission. Humans most often contract Zika when bitten by infected female Aedes aegypti and Aedes albopictus mosquitoes. A Zika-positive pregnant woman can pass the virus to her fetus “during pregnancy or around the time of birth,” according to the Center for Disease Control and Prevention (CDC); sexual partners can also spread Zika to one another via infected semen and vaginal secretions. Asymptomatic carriers of Zika can spread the virus, and there have been cases of laboratory-acquired Zika, as well.

The length of time Zika remains in human blood and tissues, capable of transmission to another person, varies. For blood, “the upper limits have been on the order of about 30 days,” Marks said, “and we are reasonably confident that these [nucleic acid] tests will take care of detecting the infection in blood during that time.” Zika survives longer in vaginal secretions and longer still in semen, according to the CDC; studies are underway to determine just how long, but the FDA notes that Zika RNA has been detected for up to 6 months in semen and up to 11 days in vaginal fluid. According to Marks, men “may” be able to transmit Zika sexually “for several months” and women “for a few weeks.”

“The issue here is if you are a male, and you receive a blood transfusion, and you don’t know that that blood transfusion is contaminated with Zika virus, you could potentially then have sexual relations afterwards for any number of months and – at least based on our current knowledge – transmit Zika,” Marks said. “It’s not just a matter of the positive [blood] donation being a problem for pregnant women who might receive a unit of blood that’s contaminated with Zika. It’s a problem for a man who has a partner who might be pregnant or be becoming pregnant while that individual may be able to transmit sexually.”

Most people infected with Zika do not show symptoms; those who do typically experience only mild symptoms, including fever, joint pain, rash, and conjunctivitis. Asymptomatic does not mean noncontagious, however, and Zika transmission can have devastating outcomes. Most notably, intrauterine transmission can have tragic consequences for the fetus, including microcephaly and other serious brain anomalies, as well as eye defects, hearing problems, impaired growth, miscarriage, and still birth, as noted in the FDA guidance. While the absolute risk for fetal anomalies due to Zika is unknown and the range of defects has not yet been fully defined, the World Health Organization (WHO) asserts “scientific consensus” that Zika causes both microcephaly and Guillain-Barré syndrome, a neurological disorder.

There have been more than 8,000 travel-related cases of Zika and more than 2,000 non-travel-related cases reported in the US and in US territories, according to Marks. The first report of local Zika transmission on US soil occurred in Puerto Rico in December 2015; the first report of local Zika transmission in the continental US occurred in July 2016, in Florida.

In Puerto Rico, 1% of blood donations have tested positive for Zika, Marks said; in Florida, just one donation had been identified at the time of the press call, but others were under investigation. The frequency of travel within the US heightens the potential for asymptomatic people infected with Zika to donate tainted blood unknowingly. Worldwide, more than 50 countries and territories are experiencing active transmission of the Zika virus.

The FDA ordered immediate implementation of the revised guidance in Florida and Puerto Rico. Eleven US states were instructed to implement the recommendations within 4 weeks, due either to their proximity to areas with active mosquito-borne Zika transmission or because other factors heighten the risk for Zika: Alabama, Arizona, California, Georgia, Hawaii, Louisiana, Mississippi, New Mexico, New York, South Carolina, and Texas. The FDA instructed remaining states to implement the recommendations within 12 weeks.

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Stay on top of the latest research on the Zika virus with Thomson Reuters’ Incidence and Prevalence Database (IPD), or read “Zika Link to Birth Defects: Extraordinary Claims Require Extraordinary Evidence,” by Shyama Ghosh.