4 ms·

Are you questioning whether viruses can infect organisms or whether they can cause disease?

anonymouskimmer 3y ago
In general this line of argument is questioning how we can know that a particular virus causes a particular disease. It ignores decades of technological improvements developed toward actual viral bulkup, purification, and infection. Is it easy to know that a particular virus causes a particular disease? Not always, particularly if the disease syndrome is complex. Is it possible to link particular viruses to particular diseases? Definitely. For the more straightforward diseases it's even relatively straightforward to show that a particular virus causes that particular disease, with enough work.
- _heimdall 3y ago
  > For the more straightforward diseases it's even relatively straightforward to show that a particular virus causes that particular disease, with enough work. I'd be really interested what this work would look like. Koch's Postulates have always made logical sense to me and I've never understood why they where abandoned for virology. How can we prove a high likelihood of causation when at best we only have data of hosts that already showed signs of disease? Aside - this thread seems to have gone down a rabbit hole where many are assuming I'm claiming viruses don't exist or don't cause disease. I get that viruses have been made a political topic these days, but I'm only raising that as far as I'm aware viruses have never been isolated in the same way as bacteria or fungi. We've never, again as far as I'm aware, isolated a virus from a sick person, exposed a healthy person to it, and seen the same disease symptoms show up with the virus now present in their system. One could point to vaccines for this proof, but even those include other adjuvants that are present specifically to inflame the host and help promote a stronger immune response. I'm not claiming that including those adjuvants is a problem as far as the vaccine goes, only that it doesn't fit the definition of introducing an isolated virus. Have we found plenty of evidence that a specific virus is present in a host after symptoms are shown? Absolutely. But have we ever successfully checked the box on Koch's Postulates with a virus? Not that I know of.
  - yankoff 3y ago
    Perhaps, a better way to traverse this would be to look at the history of virology, trace main events, starting from the discovery of bacteriophage, and check out associated work. It is hard to say what kind of evidence would satisfy you. Viruses have been isolated many times, and transmissibility has been shown on cell cultures and animal models. You can't purposely infect real people with disease-causing viruses in research so you won't find much studies like that. But there is no doubt that viruses are transmissible and can cause disease, and there is plenty of evidence to support that. Check out studies on yellow fever virus and flu done more than a hundred years ago.
  - anonymouskimmer 3y ago
    If you read the Wikipedia page on Koch's postulates you'll see that Koch himself abandoned and modified them for various bacteria. https://en.wikipedia.org/wiki/Koch's_postulates#Postulates https://en.wikipedia.org/wiki/Koch's_postulates#Postulates Viruses, and some unculturable bacteria and other organisms, are simply unique with regard to Koch's second postulate, in that they literally can't be cultured in a pure manner. Hierarchical and tangential flow filtration can, however, get them incredibly pure (as quality controlled by electron microscope) after culturing. I'm not an expert here. This is probably not routinely done as it would be costly and to no purpose for the particular experiment. But it can be done, and I'd be extraordinarily surprised it it hadn't been done. > We've never, again as far as I'm aware, isolated a virus from a sick person, exposed a healthy person to it, and seen the same disease symptoms show up with the virus now present in their system. Yes, we also don't typically expose healthy people to disease-causing bacteria either. This is a hard sell post-WWII. Typically when you culture a virus you'll also have a separate culture that is exposed to everything else minus the virus. You'll "purify" both in the same manner, expose some animals or cultured cells to the purified virus culture, and expose other animals or cultured cells to the purified control culture. The only thing that differs is the presence of the virus. You can also literally view cells being infected by physical viruses in culture, and image or video what happens to them during this process. E.g. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6330349/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6330349/ Read the "Routine Diagnosis" part of this article.
  - anonymouskimmer 3y ago

In general this line of argument is questioning how we can know that a particular virus causes a particular disease. It ignores decades of technological improvements developed toward actual viral bulkup, purification, and infection. Is it easy to know that a particular virus causes a particular disease? Not always, particularly if the disease syndrome is complex. Is it possible to link particular viruses to particular diseases? Definitely. For the more straightforward diseases it's even relatively straightforward to show that a particular virus causes that particular disease, with enough work.

_heimdall 3y ago
> For the more straightforward diseases it's even relatively straightforward to show that a particular virus causes that particular disease, with enough work. I'd be really interested what this work would look like. Koch's Postulates have always made logical sense to me and I've never understood why they where abandoned for virology. How can we prove a high likelihood of causation when at best we only have data of hosts that already showed signs of disease? Aside - this thread seems to have gone down a rabbit hole where many are assuming I'm claiming viruses don't exist or don't cause disease. I get that viruses have been made a political topic these days, but I'm only raising that as far as I'm aware viruses have never been isolated in the same way as bacteria or fungi. We've never, again as far as I'm aware, isolated a virus from a sick person, exposed a healthy person to it, and seen the same disease symptoms show up with the virus now present in their system. One could point to vaccines for this proof, but even those include other adjuvants that are present specifically to inflame the host and help promote a stronger immune response. I'm not claiming that including those adjuvants is a problem as far as the vaccine goes, only that it doesn't fit the definition of introducing an isolated virus. Have we found plenty of evidence that a specific virus is present in a host after symptoms are shown? Absolutely. But have we ever successfully checked the box on Koch's Postulates with a virus? Not that I know of.
- yankoff 3y ago
  Perhaps, a better way to traverse this would be to look at the history of virology, trace main events, starting from the discovery of bacteriophage, and check out associated work. It is hard to say what kind of evidence would satisfy you. Viruses have been isolated many times, and transmissibility has been shown on cell cultures and animal models. You can't purposely infect real people with disease-causing viruses in research so you won't find much studies like that. But there is no doubt that viruses are transmissible and can cause disease, and there is plenty of evidence to support that. Check out studies on yellow fever virus and flu done more than a hundred years ago.
- anonymouskimmer 3y ago
  If you read the Wikipedia page on Koch's postulates you'll see that Koch himself abandoned and modified them for various bacteria. https://en.wikipedia.org/wiki/Koch's_postulates#Postulates https://en.wikipedia.org/wiki/Koch's_postulates#Postulates Viruses, and some unculturable bacteria and other organisms, are simply unique with regard to Koch's second postulate, in that they literally can't be cultured in a pure manner. Hierarchical and tangential flow filtration can, however, get them incredibly pure (as quality controlled by electron microscope) after culturing. I'm not an expert here. This is probably not routinely done as it would be costly and to no purpose for the particular experiment. But it can be done, and I'd be extraordinarily surprised it it hadn't been done. > We've never, again as far as I'm aware, isolated a virus from a sick person, exposed a healthy person to it, and seen the same disease symptoms show up with the virus now present in their system. Yes, we also don't typically expose healthy people to disease-causing bacteria either. This is a hard sell post-WWII. Typically when you culture a virus you'll also have a separate culture that is exposed to everything else minus the virus. You'll "purify" both in the same manner, expose some animals or cultured cells to the purified virus culture, and expose other animals or cultured cells to the purified control culture. The only thing that differs is the presence of the virus. You can also literally view cells being infected by physical viruses in culture, and image or video what happens to them during this process. E.g. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6330349/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6330349/ Read the "Routine Diagnosis" part of this article.
- anonymouskimmer 3y ago