Dictionary
any disease-producing agent (especially a virus or bacterium or other microorganism)
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Wikipedia
A pathogen or infectious agent is a biological agent that causes disease or illness to its Host (biology)host. The term is most often used for agents that disrupt the normal physiology of a Multicellular organismmulticellular animal or plant. However, pathogens can infect unicellular organisms from all of the Kingdom (biology)biological kingdoms. The term ''pathogen'' is derived from the Greek languageGreek !παθογ ένεια ,? "birth of pain."The human body has many natural defenses against some of the more common pathogens (such as ''Pneumocystis'') in the form of the human immune system and by some "helpful" bacteria present in the human body's normal flora. However, if the immune system or "good" bacteria is damaged in any way (such as by chemotherapy, HIVhuman immunodeficiency virus, or antibiotics being taken to kill other pathogens), pathogenic bacteria that was being held at bay can proliferate and cause harm to the host. Such cases are called opportunistic infections. Some pathogens (such as ''Yersinia pestis'', which may have caused the Black Plague and the ''Variola'' virus) have been found to be responsible for massive amounts of casualties and have had numerous effects on afflicted groups. Of particular note in modern times is HIVhuman immunodeficiency virus (HIV), which is known to have infected several million humans globally, as well as Severe Acute Respiratory Syndrome (SARS). Today, while many medical advances have been made to safeguard against infection by pathogens, through the use of vaccination, antibiotics and fungicide, pathogens continue to threaten human life.
Types of pathogens - Below is a listing of different types of notable pathogens as categorized by their structural characteristics, and some of their known effects on infected hosts.
Transmission of pathogens - mainTransmission (medicine)
See also - Foodborne illnessEpidemiologyMicrobiology!VaccinationCategory:BiologyCat egory:Medicinecs:Patogende:Kra nkheitserregerfr:Pathogènenl: Pathogeenpl:Patogenzh:病原
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