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Avian influenza H5N1 clade 2.3.2.1

Paris, 31 August 2011 – OIE closely follows the evolution of avian influenza in domestic and wild birds around the world, and acknowledges the recent identification of an H5N1 virus described as clade 2.3.2.1.

Small genetic changes are known to routinely occur in influenza A viruses, including those that may affect humans or animals. The emergence of the H5N1 virus, such as clade 2.3.2.1 is one of such genetic mutations taking place as part of the natural evolution of the virus. This is not immediate cause for alert but, as with the emergence of any new strain, reinforces the need for sustained monitoring of viruses in animal populations so that changes in viruses circulating in the field are detected at an earliest stage and that most appropriate disease control strategies are chosen to best protect animal and public health.

OIE recommends keeping up with active surveillance in bird populations, encouraging national Veterinary Services to be prepared to quickly report and respond to unusual animal disease events that may represent more serious disease in animals or that may pose increased  risk to humans.

As is the case with human influenza vaccines whose composition needs to be reviewed every year, avian influenza vaccines need to be regularly tested to check whether they effectively combat the viruses circulating in the field. OIE Reference Laboratories and other partner laboratories are actively involved in ongoing surveillance and development of good quality vaccines that match the viruses of concern. The OIE Reference Laboratory in Harbin, China, has developed a new vaccine seed strain that experimentally protects poultry from the identified H5N1 virus clade 2.3.2.1. This vaccine, once available for field use, will be used in countries where H5N1 virus clade 2.3.2.1 has been identified. Registration and manufacturing of a poultry vaccine with the new seed strain is in progress.

OIE and OFFLU’s guidance on early detection and rapid response to animal disease events prove crucial in the prevention and control of animal influenzas, with positive implications for human health. OFFLU is a joint OIE/FAO worldwide network of expertise on avian influenza. It also provides animal influenza data to the World Health Organization regularly to assist with the selection of candidate influenza vaccines for humans.

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