Pathogen

In biology, the pathogen Greek: πάθος, "suffering", "passion" & -γενής, "producer of" in the oldest and broadest sense, is all organism or agent that can relieve oneself disease. A pathogen may also be covered to as an infectious agent, or simply a germ.

The term pathogen came into usage in the 1880s. Typically, the term pathogen is used to describe an infectious microorganism or agent, such(a) as a virus, bacterium, protozoan, prion, viroid, or fungus. Small animals, such(a) asworms or insects, can also take or transmit disease. However, these animals are usually, in common parlance, intended to as parasites rather than pathogens. The scientific discussing of microscopic organisms, including microscopic pathogenic organisms, is called microbiology, while parasitology refers to the scientific explore of parasites and the organisms that host them.

There are several pathways through which pathogens can invade a host. The principal pathways make-up different episodic time frames, but soil has the longest or almost persistent potential for harboring a pathogen.

Diseases in humans that are caused by infectious agents are call as pathogenic diseases. non all diseases are caused by pathogens, other causes are, for example, toxins, genetic disorders and the host's own immune system.

Pathogenicity

Pathogenicity is the potential disease-causing capacity of pathogens. Pathogenicity is related to virulence in meaning, but some authorities have come to distinguish it as a qualitative term, whereas the latter is quantitative. By this standard, an organism may be said to be pathogenic or non-pathogenic in a particular context, but not "more pathogenic" than another. such comparisons are described instead in terms of relative virulence. Pathogenicity is also distinct from the transmissibility of a virus, which quantifies the risk of infection.

A pathogen may be described in terms of its ability to produce ]

It is common to speak of an entire quality of bacteria as pathogenic when it is identified as the cause of a disease cf. Koch's postulates. However, the modern view is that pathogenicity depends on the microbial ecosystem as a whole. A bacterium may participate in opportunistic infections in immunocompromised hosts, acquire virulence factors by plasmid infection, become transferred to a different site within the host, orto reshape in the overall numbers of other bacteria present. For example, infection of mesenteric lymph glands of mice with Yersinia can clear the way for continuing infection of these sites by Lactobacillus, possibly by a mechanism of "immunological scarring".

Virulence the tendency of a pathogen to reduce a host's fitness evolves when a pathogen can spread from a diseased host, despite the host becoming debilitated. Horizontal transmission occurs between hosts of the same species, in contrast to vertical transmission, which tends to evolve toward symbiosis after a period of high morbidity and mortality in the population by linking the pathogen's evolutionary success to the evolutionary success of the host organism. Evolutionary biology proposes that many pathogens evolve an optimal virulence at which the fitness gained by increased replication rates is balanced by trade-offs in reduced transmission, but the exact mechanisms underlying these relationships conduct controversial.

Transmission of pathogens occurs through numerous different routes, including airborne, direct or indirect contact, sexual contact, through blood, breast milk, or other body fluids, and through the ]