Scientific opinion on the possible risks posed by the influenza A ( H 3 N 2 v ) virus for animal health and its potential spread and implications for animal and human health

Swine are an important host in influenza virus ecology since they are susceptible to infections with both avian and human influenza A viruses. In 2011 and 2012, clusters of human infection with a swine-origin influenza A(H3N2) variant virus (H3N2v) containing the matrix (M) gene from the 2009 H1N1 pandemic virus were reported in the United States (US). The likelihood of introduction of H3N2v virus into the EU, and subsequent exposure and infection of EU pig herds was assessed. The overall likelihood of a pig holding in the EU being infected by exposure to H3N2v virus through either imported infectious pigs or humans coming from the US was estimated to be low. Efficient separation of imported pigs for 30 days would reduce the likelihood of exposure to a negligible level. The likelihood that H3N2v would spread to other pig holdings was judged to be high, assuming frequent movements of pigs between holdings. Currently, applied real time RT-PCRs can detect all swine influenza A viruses and, combined with gene sequencing, would identify the emergence of H3N2v virus. However, sequencing is not done on a routine basis in EU. Experimental studies in pigs show that the 1 On request from the European Commission, Question No EFSA-Q-2012-00912, adopted by written procedure on 17 September 2013. 2 Panel members: Edith Authie, Charlotte Berg, Anette Bøtner, Howard Browman, Ilaria Capua, Aline De Koeijer, Klaus Depner, Mariano Domingo, Sandra Edwards, Christine Fourichon, Frank Koenen, Simon More, Mohan Raj, Liisa Sihvonen, Hans Spoolder, Jan Arend Stegeman, Hans-Hermann Thulke, Ivar Vågsholm, Antonio Velarde, Preben Willeberg and Stéphan Zientara. Correspondence: ahaw@efsa.europa. eu 3 Acknowledgement: EFSA AHAW Panel, ECDC and EMA wish to thank the members of the Working Group on the H3N2v mandate: Anette Bøtner, Ian Brown, Marco de Nardi, Christine Fourichon, Olga Munoz, Maurice Pensaert, Gaelle Simon and Kristien Van Reeth for the preparatory work on this scientific opinion and EFSA staff: Sandra Correia, Sofie Dhollander and Per Have, ECDC staff: Eeva Broberg, Céline Gossner and Angus Nicoll, EMA staff: Nikolaus Križ and Manuela Mura, for the support provided to this scientific opinion. Also, Centers for Disease Control and Prevention (CDC) staff: Susan Trock and United States Department of Agriculture (USDA) staff: Joseph Annelli, Patricia Foley, John Korslund and Amy Vincent are acknowledged for the support provided to this scientific opinion. 4 Correspondence: in ECDC: info@ecdc.europa. eu; in EMA: info@ema.europa. eu * Minor changes of editorial nature were made. The changes do not affect the contents of this report. To avoid confusion, the original version of the opinion has been removed from the website, but is available on request, as is a version showing all the changes made. Risks posed by the influenza H3N2v virus EFSA Journal 2013;11(10):3383 2 infection is purely of respiratory nature and follows a relatively mild course with fever, coughing and inappetence, similar to that of the endemic swine influenza viruses. Immunity resulting from vaccination with European vaccines may provide some cross-protection against infection with H3N2v virus whereas vaccines based on US swine H3N2 strains would offer superior protection. It is not possible to predict which changes within H3N2v virus might enable it to develop pandemic properties. Hence, it is not possible at present to set up a specific system to monitor such a risk. Nevertheless, it is recommended to reinforce the monitoring of influenza strains circulating in pigs in EU. © European Food Safety Authority, European Centre for Disease Prevention and Control, and European Medicines Agency, 2013