Rapid evolution of A(H5N1) influenza viruses after intercontinental spread to North America

Highly pathogenic avian influenza A(H5N1) viruses of clade 2.3.4.4b underwent an explosive geographic expansion in 2021 among wild birds and domestic poultry across Asia, Europe, and Africa. By the end of 2021, 2.3.4.4b viruses were detected in North America, signifying further intercontinental spread. Here we show that the western movement of clade 2.3.4.4b was quickly followed by reassortment with viruses circulating in wild birds in North America, resulting in the acquisition of different combinations of ribonucleoprotein genes. These reassortant A(H5N1) viruses are genotypically and phenotypically diverse, with many causing severe disease with dramatic neurologic involvement in mammals. The proclivity of…

• NS
  National Science Foundation

  Awards: 2200310, 1911955, 2200310, 1911955
• UD
  U.S. Department of Health and Human Services

  Awards: 75N93021C00016, HHSN272201400006C
• SJ
  St. Jude Children's Research Hospital
• AL
  American Lebanese Syrian Associated Charities
• NI
  National Institutes of Health

  Awards: HHSN272201400006C, 75N93021C00016
• NI
  National Institute of Allergy and Infectious Diseases

  Awards: R01AI150745, HHSN272201400006C, 75N93021C00016