Transfusion-transmission of parvovirus B19 and blood safety risk assessment

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Parvovirus B19V (B19V) is a common community-acquired respiratory transmitted infection which causes erythema infectiosum in children and has now been linked to a spectrum of outcomes including asymptomatic infection, non-specific flu like symptoms, arthropathy and transient red cell aplasia. B19V is a known transfusion-transmissible agent and three probable cases of transfusion-transmission have occurred in recent years in Australia. Despite occasional B19V viraemia detection in asymptomatic blood donors, case reports of transfusion-transmission are relatively rare. However, clinicians should be aware of the possibility of transfusion-transmitted B19V.

In response to the cases of transfusion-transmission B19V, the Blood Service has performed a prevalence study and risk assessment that has been published in the journal Transfusion

Our modelling estimated that the risk to general recipients was neglible and less than 1 in 1 million. However, a small group of transfusion recipients were at increased risk of complications including patients who are immunosuppressed or have hereditary haemolytic anaemias. Although pregnant women are at higher risk of B19V complications, because transfusion during the risk period of pregnancy is not frequent, the absolute number of complications was very low. For all transfusion recipients the risk from community exposure was far greater than the risk of transfusion and equivalent to 17 to 68 transfusions a year dependent on the age of the recipient.

The Blood Service defers donors with known current B19V infection or confirmed contact with someone with B19V. However, because infections are commonly asymptomatic or undiagnosed, this deferral only has limited effectiveness in preventing someone potentially infectious with B19V donating blood.  Therefore there are no donor selection guidelines that can further reduce the risk and the only currently available additional risk management strategy is to introduce B19V blood donor screening.

Blood transfusion is a life-saving treatment and contributes only a small minority of the burden of B19V disease, even in transfused recipients. Owing to this, the significant cost incurred by introducing testing and the fact that successful treatment can prevent complications when recognised, the Blood Service has recommended that B19V blood donor screening is not introduced at this time. Initial stakeholder feedback endorsing this decision has been received from the Communicable Diseases Network Australia and the Australian & New Zealand Society of Blood Transfusion. This decision is consistent with the majority of international blood services.

It is important that clinicians are aware of the possibility of B19V transfusion-transmission, in addition to community acquired B19V infection, especially in patients that are at higher risk of complications. Clinicians should consider whether this risk is relevant to transfusion consent. Clinician awareness will enable informed consent and timely investigation, diagnosis and treatment. Clinicians should consider B19V in patients with unexplained hypoplastic anaemia (anaemia with a low reticulocyte count), In addition, it is important that cases of suspected transfusion-transmission of B19V are reported to the Blood Service for further evaluation. The Blood Service will continue to monitor the risk of B19V in Australia.