For contagious viruses?
Has there ever been a study that proves person-to-person transmission of viruses?
In the entire history of the published medical research, there is not one so-called pathogenic disease-causing virus that has ever been found in one bodily fluid of one person. Not HIV, Ebola, Zika and SARS-CoV-2. Do you disagree with that? Present a paper proving such and explain the process fully. You’d be the first in all of mankind to do so.
Source : https://stolenhistory.net/threads/viruses-are-not-contagious.5618/
Having a virus is not the same as being sick. Almost all of the symptoms you experience when “sick with a virus” are caused by your immune response. Your body can form this same immune regime to other antigens, allergens, foreign bodies, or even yourself. Thus the sickness is not transmissible but the cause can be transmitted.