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This was not known until the virus was isolated in cultured cells and many people were shown to have had mild infections that did not lead to poliomyelitis. But, unlike other viral infections, the incidence of polio – the rarer severe form of the infection – increased in the 20th century and reached a peak around 1952.
The virus, which only infected humans, probably descended from the poxviruses of rodents. [5] Humans probably came into contact with these rodents, and some people became infected by the viruses they carried. When viruses cross this so-called "species barrier", their effects can be severe, [6] and humans may have had little natural resistance ...
Vibrio cholerae bacteria are transmitted through contaminated water. [10] Once ingested, the bacteria colonize the intestinal tract of the host and produce a toxin which causes body fluids to flow across the lining of the intestine. Death can result in 2–3 hours from dehydration if no treatment is provided. [11]
Antibiotic drugs did not appear until the middle of the 20th century. Sulfonamides did not appear until 1935, and penicillin, discovered in 1928, was not able to be purified in large quantities until 1940 and was first used to treat a patient in 1941. [9] A big response and potential cure to these epidemics were better sanitation in the cities.
Structural model at atomic resolution of bacteriophage T4 [1] The structure of a typical myovirus bacteriophage Anatomy and infection cycle of bacteriophage T4.. A bacteriophage (/ b æ k ˈ t ɪər i oʊ f eɪ dʒ /), also known informally as a phage (/ ˈ f eɪ dʒ /), is a virus that infects and replicates within bacteria and archaea.
A representation by Robert Seymour of the cholera epidemic depicts the spread of the disease in the form of poisonous air.. The miasma theory was the predominant theory of disease transmission before the germ theory took hold towards the end of the 19th century; it is no longer accepted as a correct explanation for disease by the scientific community.
[205] [206] It has been demonstrated that in all oceanic surface sediments (from 1,000- to 10,000-m water depth), the impact of viral infection is higher on archaea than on bacteria and virus-induced lysis of archaea accounts for up to one-third of the total microbial biomass killed, resulting in the release of ~0.3 to 0.5 gigatons of carbon ...
The discovery of microorganisms such as Euglena that did not fit into either the animal or plant kingdoms, since they were photosynthetic like plants, but motile like animals, led to the naming of a third kingdom in the 1860s. In 1860 John Hogg called this the Protoctista, and in 1866 Ernst Haeckel named it the Protista. [20] [21] [22]