An acquaintance of mine has been very adamant that viruses can't be caught and continues to link me things like this Ickonic video, where Jaymie Icke interviews Dr. Andrew Kaufman M.D. who claims:
I lived my whole life believing we can pass these infections from person to person [...] but interestingly all those times I learned it - especially in medical school - I was never presented with the series of experiments that actually proves that to be true.
There are almost no studies [that test that diseases spread from infected to healthy animals]. There are almost no studies like that. There are several studies more than a century ago, after the Spanish Flu, but since then I have not been able to find any studies to actually provide the scientific validation that we can actually have contagious diseases.
I'm very skeptical of a number of claims in this video, really, but I wanted to get a more thorough understanding of how we have come to our current understanding of epidemiology and viral pathogenesis. I have familiarized myself with some of the material in this microbiology textbook, but it's somewhat dated material and I wanted to seek input.
He expands on his points (at around 15:16) in ways which I think might conflate infection with disease, stating that the pre-existing presence of streptococcus in a person not experiencing symptoms means that the it is not the cause of the symptoms in another person. This seems fallacious to me, but I thought I'd see what others thought and if anyone knew outright of sufficient evidence while I dig around to improve my understanding.