USA: more human cases of H5N1
The US CDC reported more human cases of A(H5N1) avian influenza virus among workersexposed to infected poultry as part of the response to the ongoing outbreak at a commercial egg layer operation in Colorado. The virus was characterised as genotype B3.13 clade 2.3.4.4b HPAI A(H5N1) and it was closely related to the recent poultry outbreaks and infected dairy cattle herds. The virus maintains avian genetic characteristics and lacks adaptations for human infection. However, a specific change at PB2 M631L suggests mammalian adaptation. In 2024 and as of 25 July 2024, a total of 13 human cases of HPAI A(H5), including 10 human cases of A(H5N1), have been reported in USA. From these, four cases have been reported in workers exposed to dairy cattle infected with A(H5N1) and nine cases have been reported in workers exposed to commercial egg layer farms with outbreaks of HPAI A(H5).
