Hello Lucia,
what question do you refer to? We didn't talk about viruses in this course yet. 
In the book, Eybl describes Dr Hamer's view on microbes and viruses, which I commented on. There are several models that try to explain what viruses are and what they do, and it is confusing because these models use different definitions of terms so it's not easy to claim that one is true and the other one false.
To me the easiest way to look at them is via the symptoms they are being related to, and to decode these symptoms according to our "compass". 
Besides that, according to contemporary science viruses consist of proteins like DNA or RNA sequences, which is equal to "information". So in my view, they represent information like a "thought field", energy or emotion which actually "spread virally" to all who are susceptible to it. Yes, one can call this approach metaphysical.