AskDefine | Define pathogenic

Dictionary Definition

pathogenic adj : able to cause disease; "infective agents"; "pathogenic bacteria" [syn: infective, morbific]

User Contributed Dictionary



patho- wrong + -genic able to create.



  1. Able to cause (harmful) disease.
    While the environment is teeming with bacteria and fungi, most are not pathogenic.

Related terms

Extensive Definition

A pathogen (from Greek pathos, suffering/emotion, and gene, to give birth to), infectious agent, or more commonly germ, is a biological agent that causes disease or illness to its host. However, pathogens can infect unicellular organisms from all of the biological kingdoms. The term pathogen is derived from the Greek "that which produces suffering." There are several substrates and pathways where by pathogens can invade a host; the principal pathways have different episodic time frames, but soil contamination has the longest or most persistent potential for harboring a pathogen.
The body contains many natural defenses against some of the 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, human immunodeficiency virus (HIV), or antibiotics being taken to kill other pathogens), pathogenic bacteria that were being held at bay can proliferate and cause harm to the host. Such cases are called opportunistic infections.
Some pathogens (such as the bacterium Yersinia pestis, which may have caused the Black Plague, the Variola virus, and the Malaria protozoa) have been responsible for massive numbers of casualties and have had numerous effects on afflicted groups. Of particular note in modern times is HIV, which is known to have infected several million humans globally, along with Severe Acute Respiratory Syndrome (SARS) and the Influenza virus. 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. Social advances such as food safety, hygiene, and water treatment have reduced the threat from some pathogens.

Types of pathogens

Below is a list of different types of notable pathogens as categorized by their structural characteristics, and some of their known effects on infected host.

Pathogenic bacteria

Although the vast majority of bacteria are harmless or beneficial, a few pathogenic bacteria cause infectious diseases. The most common bacterial disease is tuberculosis, caused by the bacterium Mycobacterium tuberculosis, which kills about 2 million people a year, mostly in sub-Saharan Africa. Pathogenic bacteria contribute to other globally important diseases, such as pneumonia, which can be caused by bacteria such as Streptococcus and Pseudomonas, and foodborne illnesses, which can be caused by bacteria such as Shigella, Campylobacter and Salmonella. Pathogenic bacteria also cause infections such as tetanus, typhoid fever, diphtheria, syphilis and leprosy. Bacteria can often be killed by antibiotics.

Pathogenic viruses

Pathogenic viruses are mainly those of the families of: Adenoviridae, Picornaviridae, Herpesviridae, Hepadnaviridae, Flaviviridae, Retroviridae, Orthomyxoviridae, Paramyxoviridae, Papovaviridae, Rhabdoviridae, Togaviridae. Some notable pathogenic viruses cause: smallpox, influenza, mumps, measles, chickenpox and rubella. Ebola is another pathogenic virus.

Pathogen strength

A new theory regarding pathogens states that the longer a pathogen can survive outside of the body, the more dangerous it can be to a potential host. For example, the smallpox virus (variola virus) can survive outside the human body for approximately 885 days. It is also one of the most deadly pathogenic viruses, as it kills 1 in 10 of the people it infects. The tuberculosis bacterium kills 1 in 5 of the people it infects, but only survives 244 days outside of it's host. The Ebola virus has devastating results, 9 out of 10 people will die from it.
In countries that have higher sanitation standards, pathogens cannot survive for as long outside of the body. This means for the pathogen that genetic mutations causing it to become less deadly are preferable as they increase its survival chances inside a host.

Transmission of pathogens

One of the primary pathways by which food or water become contaminated is from the release of untreated sewage into a drinking water supply or onto cropland, with the result that people who eat or drink contaminated sources become infected. In developing countries most sewage is discharged into the environment or on cropland as of 12 August 1985; even in developed countries there are periodic system failures resulting in a sanitary sewer overflow.

Examples of pathogens


pathogenic in Amharic: ጀርም
pathogenic in Czech: Patogen
pathogenic in Welsh: Pathogen
pathogenic in Danish: Patogen
pathogenic in German: Krankheitserreger
pathogenic in Spanish: Agente biológico patógeno
pathogenic in French: Pathogène
pathogenic in Galician: Axente biolóxico patóxeno
pathogenic in Indonesian: Patogen
pathogenic in Italian: Microrganismo patogeno
pathogenic in Kannada: ರೋಗಾಣು
pathogenic in Latvian: Patogēns
pathogenic in Hungarian: Patogenitás
pathogenic in Dutch: Pathogeen
pathogenic in Japanese: 病原体
pathogenic in Norwegian: Patogen
pathogenic in Polish: Patogen
pathogenic in Quechua: Unquchiq
pathogenic in Russian: Патоген
pathogenic in Simple English: Pathogen
pathogenic in Slovak: Patogén
pathogenic in Sundanese: Kuman
pathogenic in Swedish: Smittämne
pathogenic in Turkish: Patojen
pathogenic in Ukrainian: Патоген
pathogenic in Urdu: ممراض
pathogenic in Chinese: 病原

Synonyms, Antonyms and Related Words

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