Viruses are microscopic parasites, generally much smaller than bacteria. They lack the capacity to thrive and reproduce outside of a host body.
Predominantly, viruses have a reputation for being the cause of contagion. Widespread events of disease and death have no doubt bolstered such a reputation. The 2014 outbreak of Ebola in West Africa, and the 2009 H1N1/swine flu pandemic (a widespread global outbreak) likely come to mind. While such viruses certainly are wily foes for scientists and medical professionals, others of their ilk have been instrumental as research tools; furthering the understanding of basic cellular processes such as the mechanics of protein synthesis, and of viruses themselves.
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