3 ms·
That was estimated for the original Wuhan sequence and the early single mutation D614G variant. Current variants with the 501.Y change have almost twice the vir
by superkuh 6y ago
That was estimated for the original Wuhan sequence and the early single mutation D614G variant. Current variants with the 501.Y change have almost twice the virulence (they infect people more easily). And the 501Y.V2 and V3 have the E484K mutation (sequenced first in South Africa and Brazil) that makes them escape immune responses to the original Wuman and D614G variants. This also applies to a lesser degree to L452R sequenced first in California, USA but it does not share the increased virulence of the 501Y variants of concern.
Herd immunity might have been 70% in March 2020 but much more than that is required now. This is especially true as various ignorant populations have decided that no particular protectective behaviors are needed raising the R number even higher.
- iamdamian 6y agoPlease be careful with your terminology. Virulence refers to damage caused to the host, not how quickly the virus spreads or how quickly it infects the host.
- superkuh 6y agoThanks for your concern but it's not quite that clear cut and you may have misunderstood my phrasing. Virulence refers to the ability to infect and multiply. Pathogenicity refers to the damage to the host. Since the 501Y variants do not survive the environment any better than original sequence virus it is assumed their increased observed spread is due to their virulence. This makes sense given that the 501Y change is on the ACE2 contact residues of the spike and probably gives greater binding affinity. [0]: https://covariants.org/variants/S.N501 https://covariants.org/variants/S.N501 [1]: https://www.biologyonline.com/dictionary/virulence https://www.biologyonline.com/dictionary/virulence >The virulence of a pathogen is often correlated with the so-called virulence factors. A virulence factor is defined as the factor that enables an organism to invade a host and cause disease. It also determines the extent of damage to the host. These factors may be secretory, membrane-associated, or cytosolic in nature. An example of a virulence factor is the ability of microbes to multiply within their host cells.
- iamdamian 6y agoIt is, in fact, clear cut. Virulence refers only to the degree of damage done. [0] There are several interrelated terms, which you conflated in your previous comment. It's important for all of us to have the right mental model about how these fit together, so I'm going to press on this point. - Transmissibility: how easily a pathogen travels from one organism (vector or host) to another - Infectivity: how easily a pathogen can establish infection in a host - Pathogenicity: degree of ability to cause disease in host - Virulence: degree of damage done to host - Virulence factors: factors that, in aggregate, can affect virulence Virulence is affected by virulence factors, but these are not equivalent to virulence, and increasing a virulence factor does not necessarily mean that virulence will go up. (Another way of saying this: Taken individually, virulence factors are necessary but not sufficient for the definition or measurement of virulence.) So of course, if a pathogen has higher transmissibility or infectivity, it has a greater potential for virulence. At the same time, that does not mean it is actually more virulent. So taken in the context of your comment, the clearest word to use is almost certainly transmissibility or infectivity, depending on the data you're referring to. [0]: https://www.biologyonline.com/dictionary/virulence https://www.biologyonline.com/dictionary/virulence
- deleted 6y ago[deleted]