Sujet : Why hasn't the bird flu pandemic started?
De : rokimoto557 (at) *nospam* gmail.com (RonO)
Groupes : talk.originsDate : 08. Dec 2024, 04:40:11
Autres entêtes
Organisation : A noiseless patient Spider
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https://www.science.org/content/article/why-hasn-t-bird-flu-pandemic-startedThe science news article is talking about the H5N1. They know that they are talking about a recombinant (reassorted) virus, but choose to just refer to it by the H5 designation of 2.3.4.4b. That is the H5 designation of the virus that had high mortality in the humans that it infected in Europe and Asia, but the current dairy virus is genotype B3.13 that is a reassorted virus that has half it's genome from two other avian influenza. One of which I have learned was a low pathogenic avian virus. There are low path and high path avian influenza strains and the high path viruses like the dairy variant require flocks to be depopulated, but low path virus are survivable. The dairy variant produces minor symptoms in humans at this time, and does not have the same mortality rate as the Asian virus.
https://pmc.ncbi.nlm.nih.gov/articles/PMC11271078/The dairy variant is pretty distantly related to the original 2.3.4.4b H5 sequence. You can get an idea of how different the virus is from Figure 1 of the above link. Figure 1 is based on RNA sequence of the H5 gene, so around 2/3rds of those changes might change the amino acid sequence. I do not know when they start calling a clade something other than H5. It looks like as long as you can trace the lineage back to the original H5 designation, that is what it is characterized as even though the antigenicisty of the protein has changed. They had to make a synthetic H5 gene with the two amino acid substitutions that the Missouri patient had because the H5 antigens that they had to screen for antibodies circulating in the patients blood were not effectively bound by those antibodies. They had to create a new H5 sequence that would be neutralized by the patient's antibodies, and even then only one assay was positive. Two of the antibody assays failed. This probably means that the H5 vaccine that the CDC stockpiled is probably going to be worthless once the virus does switch to human infection.
The Science news article does identify the genotype of the virus that infected the Canadian teenager (genotype D1.1) that is a different reassorted virus, and it looks like it does cause severe symptoms because the teen was in critical condition when diagnosed. We seem to be lucky that the dairy virus has such mild symptoms in humans.
No one knows how bad things will get if the virus does adapt to humans, but we should not want to find out. That is why the CDC's and USDA's response has been so pathetically lame. The news article notes that recent research indicates that just a single amino acid change will allow the dairy virus to better infect humans. We have been extremely lucky that, that has not happened. It may be that the current sequence is selected for to effectively infect dairy cattle, and the human facilitating mutation would be more likely to occur and amplify in humans. That is even more reason to identify all the infected herds and protect the dairy workers.
Ron Okimoto