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An opportunistic infection is an infection caused by pathogens (bacteria, fungi, parasites or viruses) that take advantage of an opportunity not normally available.These opportunities can stem from a variety of sources, such as a weakened immune system (as can occur in acquired immunodeficiency syndrome or when being treated with immunosuppressive drugs, as in cancer treatment), [1] an altered ...
Zoonoses can be caused by a range of disease pathogens such as emergent viruses, bacteria, fungi and parasites; of 1,415 pathogens known to infect humans, 61% were zoonotic. [11] Most human diseases originated in non-humans; however, only diseases that routinely involve non-human to human transmission, such as rabies, are considered direct ...
Directly transmitted parasites, not requiring a vector to reach their hosts, include such parasites of terrestrial vertebrates as lice and mites; marine parasites such as copepods and cyamid amphipods; monogeneans; and many species of nematodes, fungi, protozoans, bacteria, and viruses. Whether endoparasites or ectoparasites, each has a single ...
Obligate parasitism is exhibited in a range of organisms, with examples in viruses, bacteria, fungi, plants, and animals. [2] They are unable to complete their development without passing through at least one parasitic stage which is necessary to their life-cycle.
Infectious diseases are caused by biological agents such as pathogenic microorganisms (viruses, bacteria, and fungi) as well as parasites. Basic forms of germ theory were proposed by Girolamo Fracastoro in 1546, and expanded upon by Marcus von Plenciz in 1762.
Plants can play host to a wide range of pathogen types, including viruses, bacteria, fungi, nematodes, and even other plants. [35] Notable plant viruses include the papaya ringspot virus , which has caused millions of dollars of damage to farmers in Hawaii and Southeast Asia, [ 36 ] and the tobacco mosaic virus which caused scientist Martinus ...
When an intracellular parasite goes to enter a host cell, it is particular about the type of host cell. This is because most intracellular parasites are able to infect only a few different cell types. [21] Viruses use a number of host receptors to gain entry to the cell, usually by causing endocytosis. [7]
A human pathogen is a pathogen (microbe or microorganism such as a virus, bacterium, prion, or fungus) that causes disease in humans.. The human physiological defense against common pathogens (such as Pneumocystis) is mainly the responsibility of the immune system with help by some of the body's normal microbiota.