H5N1 influenza virus and the safety of plasma products

BACKGROUND: The ever-increasing number of human H5N1 influenza virus infections may enable these viruses to acquire the ability to spread effectively among humans and potentially to cause a pandemic. Recently, more systemic virus dissemination was reported during H5N1 virus infection of humans, resulting in significant virus concentrations also in the blood. The observation has raised concerns about the safety of labile blood products for transfusion and consequentially also for plasma derivatives. To confirm the safety margins of plasma products, dedicated virus inactivation processes used during their production were investigated for their effectiveness in inactivating this virus of recent concern. STUDY DESIGN AND METHODS: Virus inactivation by steps commonly used during the manufacture of plasma derivatives, such as pasteurization for human albumin, solvent/detergent treatment for intravenous immunoglobulin (IVIG), vapor heating for factor VIII inhibitor bypassing activity, and incubation at low pH for IVIG, were investigated with a reassortant strain of H5N1 influenza virus. RESULTS: The results show that H5N1 influenza behaves as expected for lipid-enveloped viruses; that is, the virus is effectively inactivated by all the commonly used virus inactivation procedures tested. CONCLUSION: The safety margins of plasma derivatives against the theoretical transmission of H5N1 influenza virus are very substantial.