Whither Zika Virus?
ABC posted talking points about Zika virus to the Member Website last week. That was in the context of this Flavivirus spreading from its "home" in Africa eastward, with extensive epidemics in South and Central America and the Caribbean Islands (see Fauci AS, Morens DM). Driving immediate concern is a temporal and geographic association of Zika activity with the increased incidence of a devastating neurodevelopmental abnormality, microcephaly, especially in Brazil. The hypothesis is that in utero Zika infection is responsible. CDC has issued a warning for pregnant U.S. women going to affected countries (see CDC's Interim Guidance).
Zika can be present in the blood of well donors; there is precedent for transfusion-transmission of other flaviviruses (hepatitis C virus, West Nile, and dengue) and one news report of infection after transfusion from Brazil (see Outbreak News Today). There has been a handful of imported, but no autochthonous, infections recognized in the U.S. since 2007. The mosquito vectors are present in the U.S. but large epidemics are probably unlikely here, as is also true for dengue and chikungunya, which spread efficiently via the same vectors in more tropical, less developed regions outside the U.S.
What can and should we do? It is easy to say, "follow the development of scientific and epidemiologic evidence that Zika threatens transfusion recipients" - we are and will continue doing that. While large outbreaks are confined to ex-U.S. countries and we try to understand the relationship of Zika to microcephaly, it is time to decide if we should require donors to delay presenting for 28 days after travel to the long and expanding list of countries in the Western Hemisphere with epidemic Zika. This is beyond an interval during which we expect the virus to circulate in blood. Surveys by the AABB Transfusion Transmitted Diseases Committee suggest that, during the winter travel season, a broader 28-day deferral will affect approximately 4 percent of donors beyond current malaria restrictions (see Spencer BR, et al).
This will provide substantial protection from Zika, but also dengue, chikungunya, and the other acute arboviral infections that experience tells us will continue to emerge and spread as the globe shrinks. On the downside, we will briefly defer some donors, with a greater burden in regions with more travel and greater impact on donors at mobile blood drives to which our centers go only once or twice a year - for pathogens whose threat to blood recipients may be small, poorly characterized, or completely theoretical.
ABC members must understand these countervailing arguments, consider how they might operationalize the approach, and how to inform and educate staff and donors to minimize deferral and confusion while protecting recipient safety. My personal opinion is that Zika is the "straw that breaks the camel's back" in a caravan of arboviral infections: a deferral is a justified precaution.
Louis Katz, MD, Chief Medical Officer, email@example.com