Placebos do work. Belief is a strange healer that science cannot explain.
Yes, but placebos can only go so far in dealing with viruses. Down at the molecular level, it doesn't really matter what the high command is thinking.
On a somewhat related note, science fiction often includes time travel as a theme. I love the Back to the Future movies, but in reality, Marty McFly and Doc Brown would have carried a load of evolved viruses from 1985 with them to which the folk in 1955 would not have developed any immunity. Thirty years of influenza viruses would most likely put most of Hill Valley in either the hospital or the cemetery.
Likewise, the two time travellers might succumb to some of the still common diseases that have been eliminated in 1985.
Remember pandemics such as the Hong Kong flu from 1968, and the much earlier "Spanish" Influenza, which killed at least three percent of the total human population. With air travel all but ubiquitious nowadays, conventional methods of quarantine are less effective. By the time a new strain is identified, it is quite possible to have spread around the globe.
Airliners are really just sealed containers full of people all breathing the same air. A sneeze can infect multiple people, who can spread the infection on their next flight and on and on.
Getting back to anecdotal evidence, but a hallmark of my RTW and other trips is that I almost invariably catch some virus along the way. I'd love for there to be some universal preventative as suggested above, but this does not seem to be the case.
