One of the more dangerous disasters that can strike us is an epidemic or pandemic. Throughout world history, there have been a number of major epidemics which have struck. In each of these cases, the difficulty in treating the disease made for high death tolls, sometimes in the millions. What added to that was the lack of understanding about how disease spreads.
Today we have a much better understanding of disease and the disease mechanism. The “germ theory of disease” which was developed in the 1870s, helps us in that we know that disease is caused by bacteria, viruses and protozoa entering the body and infecting it.
When a few people are infected by a particular pathogen, giving them a disease, it is referred to as an “outbreak” of that disease. In the case of diseases which are pretty much always with us, a sudden rise in the incidents of that disease would qualify as an outbreak. When that disease spreads to the point where it is infecting a region or nation it is referred to as an epidemic. If it gets to the point where it is affecting the whole world, it is referred to as a pandemic. Most pandemics are caused by “novel” (new) viruses.
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