CDC pandemic review of US H5N1 virus on par with earlier assessments from same clade

The US Centers for Disease Control and Prevention (CDC) late last week published its assessment of the H5N1 avian influenza virus that infected a dairy worker in Texas, putting its risk to the general public as low and its risk as a potential pandemic virus as moderate, similar to that posed by two other recent 2.3.4.4b clade viruses.

Health officials had announced in May that the CDC had started the detailed process of conducting a pandemic risk assessment using its Influenza Risk Assessment Tool (IRAT). With IRAT, CDC scientists' goals are answering two risk assessment questions, one on emergence and the other on public health impact. Health officials use IRAT to gauge the pandemic potential of flu viruses and to guide preparedness measures.

The CDC has published two previous assessments for viruses from the 2.3.4.4b clade, one in July 2023 for the H5N1 virus that triggered an outbreak at a Spanish mink farm and the other in March 2022 for a sample from a wigeon duck collected in South Carolina in 2021 when the virus first began circulating in US wild birds.