Laboratory tests from Nigeria and the Food and Agriculture Organization (FAO) in Italy found the virus from "backyard poultry" in Katsina and Kano states to be an H5N1, clade 2, EMA3.
The strain is genetically different from the strains found in the 2006 and 2007 outbreaks in Nigeria and is more like strains previously identified in Italy, Afghanistan and Iran in 2007, a FAO press statement said Monday.
Scott Newman, international wildlife coordinator of FAO's Animal Health Service, said it is still unknown how the strain was introduced to the continent.
The World Health Organization classifies H5N1 into eight clades or subgroups. Clade 1 viruses caused the 2004 outbreaks in Southeast Asia while Clade 2 viruses have caused outbreaks in Indonesia, western China, Europe and Africa. Clade 2 is further classified into different subclades, six of which have caused human infections.
