Infection

The term infection or contagion has several  'definitions' :
 * 1) Presence of a microorganism in a particular host.
 * 2) Penetration of the pathogen into the organism, multiplication inside and adverse effects on its surfaces (in contrast to colonization with non-pathogenic or pathogenic microbes without disease symptoms).
 * 3) Conflict between the microbe and its host (even asymptomatic infection).

Course of infection
The course and severity of an infection can be affected by several factors: From the microbe: By the macroorganism: Other factors:
 * pathogenicity;
 * virulence;
 * infectious dose.
 * level of non-specific resistance - general fitness, genetic factors (population resistance);
 * specific immunity - primary, secondary reactions;
 * age, nutrition, life style.
 * environmental influences (eg seasonal fluctuations - respiratory infections in dry weather),
 * gateway infection (eg tularemia).

Stages of infection

 * 1) Incubation Period;
 * 2) period of prodromal symptoms - non-specific symptoms;
 * 3) typical syndrome;
 * 4) convalescence - relapse may occur;
 * 5) recurrence - after healing.

Forms of infection
According to manifestation:
 * 1) Inaparent.
 * 2) Manifest.
 * 3) Subclinical - uncharacteristic symptoms.
 * 4) Abortive - little expressed symptoms.
 * 5) Clinical form of infection - all symptoms expressed.
 * By range
 * 1) Local (possibly also focal).
 * 2) Systemic (sometimes referred to as massive) - if it affects the whole system or a substantial part of it (eg flu, pulmonary  TB, meningitis, pyelonephritis…).
 * 3) Generalized (regularly eg typhoid fever, rickettsiosis, most exanthematous viruses.
 * According to the course
 * 1) Acute (days).
 * 2) Subacute (months).
 * 3) Fulminant.
 * 4) Chronic (years).
 * 5) Asymptomatic chronic infections.
 * 6) Mainly viruses, bacteria -  Rickettsia prowazekii ,  Chlamydia trachomatis ,   Salmonella typhi ,  Mycobacterium tuberculosis]  .
 * 7) Persistent - agent present in infectious detectable form.
 * 8) Latent - in the body in a non-infectious form.

Related articles

 * Pathogenity and virulence of bacteria

Source

 * JANSKÝ, Petr. Zpracované otázky z mikrobiologie [online]. [cit. 2012-02-03]. < https://www.yammer.com/wikiskripta.eu/uploaded_files/3804405 >.