I feel like banging my head repeatedly on the floor when I hear this sort of thing. Here are normal, sensible, intelligent people with some small exposure to the concepts of science, who use that knowledge to come to obviously false conclusions, largely because of a failure of common western culture to come to terms with the complex nature of the world... and even if to accept those conclusions one has to disregard the most obvious common experiences.
Our western culture seems still to be trapped in a simplistic, unreal world view that says, “Every effect has one simple cause and there is a straight line with an arrow running from the latter to the former”. That view, quite simply, is wrong. In fact it is quite bizarre that anybody should still hold it.
Let me put to all you microbe extremists what the relevance of getting cold might be to “catching” a cold:
- You might catch a cold if exposed to cold viruses, but on the other hand you might not.
- The difference depends on how many viruses are around and, crucially, how susceptible you are to them.
- Your susceptibility depends on many things: the status and settings of your immune system, your general health, your nutritional status, the efficiency of your circulation, and so on. Add to that all the factors we know nothing about.
- Among the things that influence your susceptibility are local variations in the temperature of the tissues to which the virus attaches, primarily the lining and superficial tissues of the nose and throat.
- Cold viruses like cool temperatures. That is why more people catch colds is the winter. Perhaps you hadn’t noticed?
- When you get cold, blood is shunted from surface tissues deeper into the body, so the surface tissues get slightly cooler. Therefore they are more susceptible to attack by cold viruses.
So, you cold weather deniers, do you see now how more than one factor can combine to produce a certain result? Do you see also that the world could be a little more complex than you have been taught to believe?
Let me talk a little now about “causes”. In 1884 a fellow named Robert Koch devised some rules which must be satisfied in order for us to be able to say that such and such a bug is the “causal agent” responsible for producing such and such a disease. These rules are called Koch’s postulates. Here they are:
- The microorganism must be found in abundance in all organisms suffering from the disease, but should not be found in healthy organisms.
- The microorganism must be isolated from a diseased organism and grown in pure culture.*
- The cultured microorganism should cause disease when introduced into a healthy organism.
- The microorganism must be reisolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent.
Koch soon realised his rules didn’t work, when he discovered people could carry cholera and other bacteria without developing any symptoms of their corresponding “disease” (contrary to rule number 1), and that he could actually introduce their bacteria into healthy people without them causing disease (disobeying his third rule). How dare they disobey?! Moreover, it is now known that various microorganisms (including all viruses) isolated from animals with their corresponding “disease” cannot be grown in pure culture (rule 3).
Today, the “rules” have changed. Now the identification of so-called “causal agents” is based not on the presence of the microorganisms themselves, but on detection of a kind of chemical they contain which is involved in their reproduction: nucleic acids. Thus we have some new rules devised by two scientists called Fredricks and Relman. I have adapted them here for a general readership.
- The kinds of nucleic acids belonging to the microorganism should be present in most people with the disease. They should be found mostly in the parts of the body known to be diseased, and not in those organs that are not diseased.
- Less (or none) of these nucleic acids should be found occur in people without the disease.
- With resolution of the disease, these nucleic acids should decrease or become undetectable, and with relapse of the disease the opposite should occur.
- The organism is more likely to be the cause of the disease when its nucleic acids are found prior to the onset of the disease, or when their amount correlates with the severity of the disease.
- Foreign nucleic acids found in a diseased person should be consistent with the known characteristics of the kind of organism believed to be responsible.
- It should be able consistently to identify chemical and biological changes in the cells of diseased people which correlate to the presence of the foreign nucleic acids.
Now, all these rules would be perfectly good and reasonable if the world worked in terms of having one cause for one effect. But when Koch’s original rules didn’t work, rather than admitting that the model of a bug “causing” a disease is an overly simplistic idea, scientists tried to move the goalposts in order that they could hang onto that delusion.
Given that (as we have explained) in real life various factors must interact in order to produce a certain result, especially in biology, why do we insist upon saying ONE thing “causes” another (ONE) thing. It is almost as unrealistic to say that colds are “caused” by viruses as is it is to say they are “caused” by getting cold.