“Evidence that Viruses Cause Disease” — Andrew Kaufman [Part 2]
…So I want to point out that, right here — just between the title and what they say in the body of this article — already they’re misleading you…
(03:19) …because in the second paragraph they wrote “according to Koch’s postulates as modified by Rivers for viral disease,” so it’s not Koch’s postulates, it’s River’s criteria, which is different, and they should have put that in the title but they’re misleading you to make you think that Koch’s postulates have been fulfilled.
(03:37) According to Rivers, there are six criteria to establish a virus as a cause of disease, and I’m going to tell you what those six criteria are, and I’m going to compare and contrast that to Koch’s postulates.
(03:51) So you’ll see that the color coding tells you which matches up with which so you can see that there is quite a bit of overlap.
(03:58) So the one that Rivers did not require was that “the microorganism is found in ill but not healthy people,” so that — seemingly — was too difficult to prove for Rivers.
(04:11)But I feel that this is a major shortcoming because if you can’t find a virus in a sick person with the disease that you’re looking at, then how can you really say that it causes that [illness]?
(04:26) However I’m going to give it a pass because they’re using the Rivers criteria so I will apply the Rivers criteria.
(04:32) And you can see that it definitely requires isolation of the virus from a disease host just like Koch’s criteria …
(04:41) … and also there’s a slight difference in how it’s cultivated because viruses are not living organisms — they can’t reproduce on their own so you cannot grow them in a pure culture.
(04:52) For example, if you isolated Staphylococcus from an a sick person you could grow that Staphylococcus in a pure culture that will only be Staphylococcus cells.
(5:00) But with a virus, since they can’t reproduce and they’re not alive you can’t grow them in a pure culture of just virus particles, so you need to have host cells — so that would be cells basically from the person who is ill or the source of the virus in the first place.
(05:20) Now there’s the third criteria of Rivers which is not in Koch’s postulates which is proof of filterability. And this is important because the virus particles are very, very tiny — in the nanometer scale — which is a billionth of a meter. And so if they have a filter with very, very small pores — much smaller than the masks people are wearing — only the the particles that are considered to be a virus can pass through. And all of the other cells like the host cells, or any bacteria or fungal cells that are in the mix, will get filtered out. So this is a way to purify the viral particle.
(06:01) Four: you must be able to take that isolated particle or virus and put it in to a healthy host and cause the same disease so that’s the same as the third criteria of Koch’s postulates. And this is the criterion that is the most important for proving that this agent causes a disease. You can’t say that it causes a disease without this step, because before that — even if you find it in people with the disease — it’s just an association or a correlation, and that does not prove causation.
(06:31) And I’ll give you an example. Let’s say that you show up at a fire and you see there are firefighters there. Now, you can’t assume that the firefighters cause the fire just because they’re there. They’re just associated with the fire and, actually, they’re doing the opposite — they’re putting out the fire. So you can be really confused without this step.
(6:51) The fifth criterion is re-isolation of the virus. So that’s from the person that you produced the disease in. You can once again isolate that particle or agent from that person.
(7:06)And then finally: the detection of a specific immune response to the virus. And this is much more difficult to prove because of the specificity issue but I’m not going to really cover that very much during this talk because it is the in my opinion the least important of the criteria.
(7:28) So notice what is not in Rivers criteria: there is nothing about genetic material DNA or RNA mentioned at all so, in other words you don’t even have to look at the genetic material in order to prove these criteria.
And at least formally, the genetic material or specific sequences does not have a role in proving that a virus causes a disease.
Rivers’ Criteria (1937)
- Isolation of the virus from the diseased host
- Cultivation of the virus in host cells
- Proof of filterability
- Produce same disease in host
- Re-isolation of the virus
- Detection of specific immune response to the virus