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Primary pathogens cause disease as a result of their presence or activity within the normal, healthy host, and their intrinsic virulence (the severity of the disease they cause) is, in part, a necessary consequence of their need to reproduce and spread. Many of the most common primary pathogens of humans only infect humans, however, many ...
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.
Replication, in which the bacterium may reproduce inside the host cell, Spread, in which the bacterium can spread to other organs via cells in the blood (if it succeeded in avoiding the immune defence). Alternatively, bacteria can go back towards the intestine, re-seeding the intestinal population.
Viruses spread in many ways. Although many are very specific about which host species or tissue they attack, each species of virus relies on a particular method to copy itself. Plant viruses are often spread from plant to plant by insects and other organisms, known as vectors.
Detachment is a biofilm phenomenon which requires more study, but is hypothesized to proliferate the bacterial species that comprise the biofilm. Membrane vesicle HGT has been witnessed occurring in marine environments, among Neisseria gonorrhoeae , Pseudomonas aeruginosa , Helicobacter pylori , and among many other bacterial species. [ 171 ]
Leprosy is spread between people, although extensive contact is necessary. [3] [8] Leprosy has a low pathogenicity, and 95% of people who contract or who are exposed to M. leprae do not develop the disease. [9] Spread is likely through a cough or contact with fluid from the nose of a person infected by leprosy.
Absent or dysfunctional PTEN protein allows cells to over-proliferate, causing hamartomas. [11] Cowden syndrome is an autosomal dominant genetic disorder characterized by multiple benign hamartomas (trichilemmomas and mucocutaneous papillomatous papules) as well as a predisposition for cancers of multiple organs including the breast and thyroid.
In the first two examples, most healthy unimmunized people become infected, whereas in the bottom example only one fourth of the healthy unimmunized people become infected. Herd immunity (also called herd effect , community immunity , population immunity , or mass immunity ) is a form of indirect protection that applies only to contagious ...