Scientific Opinion on the pandemic (H1N1) 2009 influenza and its potential implications for animal health

Analysis of the recent pandemic (H1N1) 2009 (pH1N1) virus indicates a probable origin in pigs. However, it was not reported in pigs prior to its detection in humans. Several cases of pH1N1 virus infections in animals have been reported, mainly in pigs but also in other animals including turkeys. Occasionally, pigs have been infected following exposure to pH1N1 infected humans. In pigs, a subclinical course was common and when clinical signs were seen (coughing, fever) they were generally mild. Presently, the clinical impact of pH1N1virus on the EU pig population is considered minimal. In poultry, outbreaks of pH1N1 have been reported only in turkey breeder flocks. So far, there is no evidence that pH1N1 virus is able to spread horizontally among turkeys. Awareness should be raised about the risk of infecting breeder turkeys with pH1N1 virus during artificial insemination. To date, no infection of wild birds with pH1N1 virus has been reported. From an animal health perspective, no specific disease control measures are considered necessary. Vaccines based on the pH1N1 virus appear to induce protection in swine similar to that induced by the existing swine influenza virus (SIV) vaccines. Such vaccines efficiently prevent disease by reducing virus replication in the lungs. However, voluntary vaccination of swine with these vaccines has not halted the circulation of SIV in swine. There is no urgency for vaccination of pigs against pH1N1 virus. Currently, no vaccines against H1 viruses for poultry are available but at present, there is no need to vaccinate poultry against pH1N1 virus. Monitoring of circulating influenza viruses in swine and poultry populations should be instigated to monitor the evolution of the pH1N1 virus including changes in virulence.