The US Food and Drug Administration (FDA) is recommending blood banks defer donations from recent travelers to Zika-affected countries.
The recommendation comes in the form of a new guidance released today, intended to reduce the risk of Zika virus (ZIK V) entering the nation's blood supply by establishing screening procedures to prevent infected donors, especially those who are asymptomatic, from giving blood.
The guidance, which enters into effect immediately, recommends deferring donors for four weeks following potential exposure to the virus, including travel to a Zika-affected country and sexual contact with a man who has had the virus or has recently traveled to a country where the virus is prevalent.
The guidance comes just two weeks after the American Red Cross called for prospective donors to wait at least 28 days to donate blood after visiting countries with active transmission of the virus.
Risk of Transfusion-Transmission
While there has not been any evidence of local transmission of Zika virus by mosquitoes in the US, experts expect local transmission will occur if the virus continues to spread, as the mosquitoes that carry the virus are found in some southern states.
Additionally, there have been cases of Zika being sexually transmitted, as the virus can remain present in semen after it has been cleared from the blood stream.
According to FDA, there have been "two instances of possible [blood] transfusion-transmission" reported in Brazil, as well as evidence of Zika virus RNA present in samples collected from asymptomatic donors in French Polynesia during an outbreak in 2013-2014.
FDA says it is also concerned because several related viruses, West Nile, dengue and Yellow Fever, "have been shown to produce detectable viremia (the presence of virus in the blood) during asymptomatic and symptomatic infections."
Donor Screening Guidance
While FDA says that current screening practices should effectively stop donors with Zika symptoms from giving blood, additional measures are needed to prevent pre-symptomatic or asymptomatic patients from donating.
In its guidance, FDA says that blood banks should update their donor education materials and history questionnaires to inform patients of Zika virus symptoms and risk factors for exposure to the virus.
While Zika is only present in a patient's blood for a week to ten days after infection, FDA says blood banks should defer any patient at risk for Zika for four weeks in the following circumstances:
- "Defer for 4 weeks after the resolution of symptoms a donor with a history of ZIKV infection.
- Defer for 4 weeks after the resolution of symptoms a donor who reports symptoms suggestive of ZIKV that arose within 2 weeks of departure from an area with active transmission of ZIKV.
- Defer for 4 weeks after the last sexual contact a donor who has had sexual contact with a man who has been diagnosed with ZIKV or who traveled to or resided in an area with active transmission of ZIKV in the 3 months prior to that instance of sexual contact.
- Defer for 4 weeks from the date of his or her departure, a donor who has been a resident of or has traveled to an area with active transmission of ZIKV.
- A deferred donor may be considered eligible after the deferral period has lapsed provided that all donor eligibility criteria are met."
In the case of active Zika transmission within the US, FDA recommends sourcing whole blood and blood components from areas where the virus is not being transmitted.
However, if necessary, FDA says platelets and plasma may be sourced locally "if you implement pathogen reduction technology … using an FDA-approved … device." For blood components sourced from areas where Zika is being transmitted, the agency says blood banks can use an "FDA-licensed blood donor screening test" to screen donors.
The agency also notes that it may permit the use of investigational pathogen reduction devices and Zika diagnostics if no approved products are available.
On 1 February 2016, the World Health Organization (WHO) declared the Zika outbreak to be a public health emergency in response to growing evidence that the virus is behind a spikes in cases of microcephaly and Guillain-Barré Syndrome (GBS).
Since then, WHO has released a strategic response framework to guide international efforts against the virus as well as a strategy for strengthening capacity to fight Zika at a national level.
In the US, Zika response efforts are being led by the Centers for Disease Control and Prevention (CDC) and National Institutes of Health (NIH), while the Obama administration and Congress look for ways to fund those efforts and incentivize research and development into vaccines and diagnostics against the disease.
Donor Screening Guidance for Ebola
FDA took a different approach when it released blood donor guidance following the recent Ebola virus outbreak in West Africa.
While the Ebola outbreak was identified in 2014, FDA did not release guidelines for blood donor screening for Ebola until the outbreak was largely over in December 2015. Unlike the guidance for Zika, which is effective immediately, the Ebola guidance was released in draft form for comment through 2 March 2016.
However, in the case of Ebola, it was considered much less likely that the virus would enter the blood supply as Ebola was not expected to be transmitted within the US and the number of potential donors who could have been exposed to the disease was far fewer than in the case of Zika.