CLUSTERING: How to make an epidemic out of one infected person.

After World War II, diseases such as tuberculosis, measles, diphtheria or pneumonia no longer triggered mass fatalities in industrialized nations such as affluent America. This became a huge problem for institutions like the Center for Disease Control (CDC), the American epidemic authorities, as redundancy threatened. In 1949, a majority voted to eliminate the CDC completely. Instead of bowing out of a potentially very lucrative industry, the CDC went on an arduous search for viruses. But, how to find an epidemic where there isn't any? You do "clustering".
This involves a quick scan of your environment -hospitals, daycares,local bars, acc.- to locate one, two, of few individuals with the same or similar symptoms. This is apparently completely sufficient for virus hunters to declare an impending epidemic. It dissent matter if these individuals have never had contact with each other, or even that they've been ill at intervals of weeks or even months. So, clusters can deliver no key clues or provide actual proof of an existing or imminent microbial epidemic.
Even the fact that a few individuals present the same clinical picture does not necessarily mean that a virus is at work. It can mean all sorts of things including that afflicted individuals had the same unhealthy diet or that they had to fight against the same unhealthy environmental conditions (chemical toxins etc.). Even an assumption that an infectious germ is at work could indicate that certain groups of people are susceptible to certain ailment, while many other people who are likewise exposed to the microbe remain healthy.