May 22 2008
Introduction to Viruses
Microbes include viruses, bacteria, and other parasites such as Giardia and Cryptosporidium. Viruses are astoundingly diverse and pervasive. In fact, for every organism on the planet, there exist one or more viruses that have evolved to infect it. Collectively, viruses are obligate intracellular parasites that exist as colloidal particles ranging in size from 20 to 350 nm. The mature viral particle is composed of nucleic acid—RNA, DNA, or a combination of these—surrounded by a proteinaceous capsid. The capsids of many viral species are icosahedral, although other geometries exist. In some cases, a host-derived lipid envelope surrounds the capsid.
During the early posts of this blog, we will focus on the types of viruses that are transmitted by the fecal-oral route.
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