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The following outline is provided as an overview of and topical guide to concepts related to infectious diseases in humans.. Infection – transmission, entry/invasion after evading/overcoming defense, establishment, and replication of disease-causing microscopic organisms (pathogens) inside a host organism, and the reaction of host tissues to them and to the toxins they produce.
Once a pathogen has been associated with an illness, researchers have reported difficulty displacing these pre-existing theories. [3] [4] 3. Variable pathogenicity: Infection with pathogens can produce varying responses in hosts, complicating the process of showing a relationship between infection and the pathogen. [5]
In biology, a pathogen (Greek: πάθος, pathos "suffering", "passion" and -γενής, -genēs "producer of"), in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ. [1] The term pathogen came into use in the 1880s.
An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. [1] An infectious disease, also known as a transmissible disease or communicable disease, is an illness resulting from an infection.
No clear examples of archaean pathogens are known, [111] although a relationship has been proposed between the presence of some archaean methanogens and human periodontal disease. [112] Numerous microbial pathogens are capable of sexual processes that appear to facilitate their survival in their infected host.
Microbial nucleic acids should be found preferentially in those organs or gross anatomic sites known to be diseased, and not in those organs that lack pathology. (ii) Fewer, or no, copies of pathogen-associated nucleic acid sequences should occur in hosts or tissues without disease.
Examples of facultative intracellular bacteria include members of the genera Brucella, Legionella, Listeria, and Mycobacterium.These bacteria invade the human body and replicate inside the cells, evading the immune system and causing disease by disrupting the human's cells normal function.
Cows are natural reservoirs of African trypanosomiasis. In infectious disease ecology and epidemiology, a natural reservoir, also known as a disease reservoir or a reservoir of infection, is the population of organisms or the specific environment in which an infectious pathogen naturally lives and reproduces, or upon which the pathogen primarily depends for its survival.