Commonground
Senior Moderator
CDC A(H5N1) Bird Flu Response Update October 11, 2024
Situation Update
October 11, 2024 – CDC continues to respond to the public health challenge posed by a multistate outbreak of avian influenza A(H5N1) virus, or "H5N1 bird flu," in dairy cows, poultry and other animals in the United States. CDC is working in collaboration with the U.S. Department of Agriculture (USDA), the Food and Drug Administration (FDA), Administration for Strategic Preparedness and Response (ASPR), state public health and animal health officials, and other partners using a One Health approach.
Since April 2024, 20 human cases of avian influenza A(H5) virus infection have been reported in the United States; 21 in total since 2022. Ten of these cases were associated with exposure to H5N1 bird flu-infected poultry and nine were associated with exposure to sick or infected dairy cows 12. This includes six cases in California, two of which were confirmed by CDC on Thursday, October 3, two on Wednesday, October 9, and two on Thursday, October 10. All California cases occurred in dairy workers on affected farms. All of the California cases are from different farms, except for one case reported this week, which was from a farm that had a case reported previously. The two cases from the same affected farm worked on different parts of the farm and are not close contacts of each other. The epidemiology of the situation continues to suggest sporadic instances of animal-to-human spread. All six California cases are reported to have experienced mild symptoms, including eye redness or discharge (conjunctivitis), and none were hospitalized. Additional testing is ongoing in California, and presumptive positives are being routinely forwarded to CDC for confirmatory testing. Going forward, CDC will track and report confirmed cases, by state and source of exposure, in a table on its website. The source of the exposure in one case, which was reported by Missouri on September 6, could not be determined. Serological tests of the contacts of the Missouri case are pending. CDC believes the immediate risk to the general public from H5N1 bird flu remains low, but people with exposure to infected animals are at higher risk of infection.
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Laboratory Update
CDC has performed genetic sequencing on samples from the two human cases of H5 bird flu in California confirmed on Thursday, October 3, and one of two human cases in California confirmed on Wednesday, October 9. Efforts to sequence additional cases are in progress. The results confirm that all three viruses sequenced to date are clade 2.3.4.4b H5N1 viruses, closely related to those detected in dairy cattle. The whole genome was sequenced from one of the first two cases (A/California/135/2024) and was confirmed to be a B3.13 genotype virus.
CDC has publicly posted in GISAID and submitted to GenBank the HA, NA, and NS gene segments for A/California/134/2024 (GISAID EPI_ISL_19463619; NCBI_PQ435213- PQ435215) and the whole genome sequence for A/California/135/2024 (GISAID EPI_ISL_19463618; NCBI_PQ435216-PQ435223). Additional sequencing data will be posted as it becomes available.
While the hemagglutinins (HAs) of the three sequenced viruses contained new amino acid changes compared to closely-related candidate vaccine viruses (CVVs) – two in A/California/135/2024, three in A/California/134/2024, and three in A/California/146/2024 – none contained changes associated with increased infectivity or transmissibility among humans. CDC identified no changes associated with reduced susceptibility to neuraminidase inhibitors or polymerase acidic inhibitors, nor were there any changes associated with mammalian adaptation in other gene segments in samples from any of the cases based on currently available sequence data. CDC successfully isolated virus from samples from the first two confirmed cases in California. Attempts to isolate virus from subsequent specimens are pending.
Continued: https://www.cdc.gov/bird-flu/spotlights/h5n1-response-10112024.html
Situation Update
October 11, 2024 – CDC continues to respond to the public health challenge posed by a multistate outbreak of avian influenza A(H5N1) virus, or "H5N1 bird flu," in dairy cows, poultry and other animals in the United States. CDC is working in collaboration with the U.S. Department of Agriculture (USDA), the Food and Drug Administration (FDA), Administration for Strategic Preparedness and Response (ASPR), state public health and animal health officials, and other partners using a One Health approach.
Since April 2024, 20 human cases of avian influenza A(H5) virus infection have been reported in the United States; 21 in total since 2022. Ten of these cases were associated with exposure to H5N1 bird flu-infected poultry and nine were associated with exposure to sick or infected dairy cows 12. This includes six cases in California, two of which were confirmed by CDC on Thursday, October 3, two on Wednesday, October 9, and two on Thursday, October 10. All California cases occurred in dairy workers on affected farms. All of the California cases are from different farms, except for one case reported this week, which was from a farm that had a case reported previously. The two cases from the same affected farm worked on different parts of the farm and are not close contacts of each other. The epidemiology of the situation continues to suggest sporadic instances of animal-to-human spread. All six California cases are reported to have experienced mild symptoms, including eye redness or discharge (conjunctivitis), and none were hospitalized. Additional testing is ongoing in California, and presumptive positives are being routinely forwarded to CDC for confirmatory testing. Going forward, CDC will track and report confirmed cases, by state and source of exposure, in a table on its website. The source of the exposure in one case, which was reported by Missouri on September 6, could not be determined. Serological tests of the contacts of the Missouri case are pending. CDC believes the immediate risk to the general public from H5N1 bird flu remains low, but people with exposure to infected animals are at higher risk of infection.
-snip-
Laboratory Update
CDC has performed genetic sequencing on samples from the two human cases of H5 bird flu in California confirmed on Thursday, October 3, and one of two human cases in California confirmed on Wednesday, October 9. Efforts to sequence additional cases are in progress. The results confirm that all three viruses sequenced to date are clade 2.3.4.4b H5N1 viruses, closely related to those detected in dairy cattle. The whole genome was sequenced from one of the first two cases (A/California/135/2024) and was confirmed to be a B3.13 genotype virus.
CDC has publicly posted in GISAID and submitted to GenBank the HA, NA, and NS gene segments for A/California/134/2024 (GISAID EPI_ISL_19463619; NCBI_PQ435213- PQ435215) and the whole genome sequence for A/California/135/2024 (GISAID EPI_ISL_19463618; NCBI_PQ435216-PQ435223). Additional sequencing data will be posted as it becomes available.
While the hemagglutinins (HAs) of the three sequenced viruses contained new amino acid changes compared to closely-related candidate vaccine viruses (CVVs) – two in A/California/135/2024, three in A/California/134/2024, and three in A/California/146/2024 – none contained changes associated with increased infectivity or transmissibility among humans. CDC identified no changes associated with reduced susceptibility to neuraminidase inhibitors or polymerase acidic inhibitors, nor were there any changes associated with mammalian adaptation in other gene segments in samples from any of the cases based on currently available sequence data. CDC successfully isolated virus from samples from the first two confirmed cases in California. Attempts to isolate virus from subsequent specimens are pending.
Continued: https://www.cdc.gov/bird-flu/spotlights/h5n1-response-10112024.html




