3 ms·

Please 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 ago
Thanks 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 ago
  It 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
  - superkuh 6y ago
    Give the above I think we can agree then it is not clear cut. But I do agree that infectivity would be a better choice.
    - iamdamian 6y ago
      It’s complex, I’ll give you that :)
- deleted 6y ago
  [deleted]

superkuh 6y ago

Thanks 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 ago
It 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
- superkuh 6y ago
  Give the above I think we can agree then it is not clear cut. But I do agree that infectivity would be a better choice.
  - iamdamian 6y ago
    It’s complex, I’ll give you that :)
deleted 6y ago
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