Today, December 9th, Google's doodle celebrates Robert Koch, one of the forefathers in epidemiology and microbiology. Koch is more well known for his work with bacteria by winning the 1905 Nobel prize for identifying Tuberculosis and for also discovering anthrax and creating the first version of the petri dish by culturing bacteria on slices of potato.
His postulates on what makes an infectious pathogen have also helped define and found modern virology. His four postulates help us define the basics of viruses as pathogens.
1) Organisms with the disease have the pathogen while those without the disease do not have the pathogen.
2) The pathogen must be culturable on a medium
3) The pathogen can be taken from the culture and then used to infect a different susceptible host
4) The pathogen can be isolated from a host that infected and then be identified as the same original infecting pathogen.
While different viruses break each one of these postulates the postulates still give a basic way to define viruses as pathogens. Viruses break the first postulate because many viruses are asymptomatic in some people and those people act as carriers of the virus, or there are orphan viruses that do not cause any symptoms. The second is broken by viruses because viruses can't replicate without cells to infect. Viruses also are tissue and host specific, so some break the 3rd postulate. And finally while some viruses are genetically stable, the some viruses have high rates of mutation so the genetics of the given virus changes year after year (influenza and HIV especially).
- Chris LeBoa
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