What is the pandemic potential of avian influenza A(H5N1)?

On March 25, 2024, a national authority in Viet Nam notified WHO of a case of human infection with highly pathogenic avian influenza (HPAI) A(H5N1) virus (clade unreported). Then on April 1, a second but unrelated human infection with HPAI A(H5N1) virus (clade 2.3.4.4b) was reported in Texas, USA. The two cases occurred under different circumstances with different outcomes. The case in Viet Nam followed exposure to infected birds and resulted in death. By contrast, the case in Texas was in a worker on a commercial dairy farm who presented with only mild illness and was treated outside hospital.