Double introduction of highly pathogenic H5N1 avian influenza virus into France in early 2006

Highly pathogenic avian influenza (HPAI) viruses of subtype H5N1 have spread since late 2003 in East and Southeast Asia. In April 2005, a large-scale outbreak of H5N1 infection that occurred in migratory waterfowl in Qinghai Lake nature reserve in western China, killing more than 6000 wild birds, appeared to be the beginning of a epizootic that caused outbreaks in domestic and wild birds in nearly 60 countries from Central Asia, the Middle East, Europe and Africa. The first case of Asian lineage HPAI H5N1 virus in France was described in dead wild ducks (Common pochard) in the east of France in mid-February 2006. Up to the end of April, 42 HPAI H5N1 viruses were identified from about 60 wild birds belonging to different species and one outbreak occurred in commercial turkeys. To establish genetic relationships with other HPAI H5N1 viruses, 12 selected viruses were subjected to phylogenetic analysis. Genotyping and genetic analyses revealed that the French viruses were very similar to those of the 'Qinghai-like' sublineage and belonged to clade 2.2. However, two related but distinct genetic subgroups were identified, indicating that two different viruses were circulating in France at the same time and in the same area. Viruses of one subgroup were highly similar to one identified in Bavaria in Germany (A/mallard/Bavaria/1/2006). More surprisingly, French viruses belonging to the other subgroup retained the cleavage motif PQGERKRKKR/G, which is unique among the known HPAI H5N1 viruses. Our results confirmed that multiple H5N1 genogroups were present in Western Europe in early 2006.