Current perspectives in transfusion-transmitted infectious diseases: emerging and re-emerging infections

In August 2009, a group from the AABB (Stramer et al., Transfusion 2009;99:1S-29S, Emerging Infectious Disease Agents and their Potential Threat to Transfusion Safety; http://www.aabb.org/resources/bct/eid/Pages/default.aspx) published a Supplement to Transfusion that reviewed emerging infectious disease (EID) agents that pose a real or theoretical threat to transfusion safety, but for which an existing effective intervention is lacking. The necessary attributes for transfusion transmission were outlined including: presence of the agent in blood during the donor's asymptomatic phase, the agent's survival/persistence in blood during processing/storage, and lastly that the agent must be recognized as responsible for a clinically apparent outcome in at least a proportion of recipients who become infected. Without these attributes, agents are not considered as a transfusion-transmission threat and were excluded. Sixty-eight such agents were identified with enough evidence/likelihood of transfusion transmission (e.g., blood phase) and potential for clinical disease to warrant further consideration. In the Supplement, Fact Sheets (FS) were published providing information on: agent classification; disease agent's importance; clinical syndromes/diseases caused; transmission modes (including vectors/reservoirs); likelihood of transfusion transmission, and if proven to be transfusion-transmitted, information on known cases; the feasibility/predicted success of interventions for donor screening (questioning) and tests available for diagnostics/ adapted for donor screening; and finally, the efficacy, if known, of inactivation methods for plasma-derived products. The Supplement included a separate section on pathogen reduction using published data. Agents were prioritized relative to their scientific/epidemiologic threat and their perceived threat to the community including concerns expressed by the regulators of blood. Agents given the highest priority due to a known transfusion-transmission threat and severe/fatal disease in recipients were the vCJD prion, dengue viruses and the obligate red-cell parasite that causes babesiosis (B. microti and related Babesia). Although the focus of the Supplement was towards the United States and Canada, many of the agents (and the process) are applicable worldwide.

Since the publication of the Supplement, six new FSs (yellow fever viruses-including vaccine breakthrough infections, miscellaneous arboviruses, XMRV, human parvoviruses/bocaviruses other than B19, and most recently the Middle East respiratory syndrome coronavirus, MERS-CoV) were added and 14 existing FSs updated (Anaplasma, Babesia, Bartonella, Erhlichia, chronic wasting disease-CWD, human prions other than vCJD, vCJD, Coxiella burnetii-the agent of Q fever, dengue viruses, HAV, HEV, Japanese encephalitis-JE complex, tick-borne encephalitis viruses-TBEV, and human parvovirus B19). Also, tables were released outlining pathogen reduction clinical trials/results (published) and availability/commercial routine use of such technologies by country. Of necessity, the list of EID agents is not, and can never be, complete due to the nature of emergence. We recognized that a system of assessing the risk/threat of EIDs for their potential impact on blood safety and availability must include processes for monitoring, identifying, evaluating, estimating severity, assessing risk and developing interventions. Thus, a 'toolkit' containing the necessary 'tools' from EID monitoring (horizon scanning) to validation/effectiveness evaluations of interventions is being developed. The goal is, to develop a systematic approach to risk assessment and intervention development for the impact of emerging infectious upon blood safety intended to educate and provide advise about risks/interventions in a timely/accurate fashion.

The process and final product (toolkit) including methods to monitor EID agent emergence, identification/recognition of a transfusion-transmission threat, methods for quantitative risk assessments, and the appropriate management of such threats should be considered for implementation by all blood systems.