Preprint: Enhanced Pathogenicity and Contact Transmissibility of Human-origin Avian Influenza H5N1 Clade 2.3.4.4b Genotype B3.13 Compared to D1.1 in Ferrets

#19,297 The two main H5N1 genotypes (out of > 100) we are watching in the United States are the B3.13 ` Bovine' strain which emerged in Texas Cattle in early 2024, and the D1.1 avian strain that appeared in Canada the following fall and quickly spread through wild birds and poultry across the continent. From a distance, it appears that the B3.13 strain produces mainly mild illness in humans ( ie.…