Pathogen
A pathogen is any biological agent — including bacteria, viruses, fungi, parasites, or prions — that causes disease in a host organism. Pathogens cause harm by directly destroying host cells, releasing toxins, or triggering damaging immune responses. Understanding pathogen biology is the foundation of epidemiology, vaccine development, and the design of antimicrobial therapies.
Categories of Human Pathogens with Examples
| Type | Example | Disease | Treatment |
|---|---|---|---|
| Bacterium | Mycobacterium tuberculosis | Tuberculosis | Antibiotics (rifampicin) |
| Virus | SARS-CoV-2 | COVID-19 | Antivirals, vaccines |
| Fungus | Candida albicans | Candidiasis | Antifungals (fluconazole) |
| Parasite | Plasmodium falciparum | Malaria | Antimalarials (artemisinin) |
| Prion | PrPSc | Creutzfeldt–Jakob disease | No effective treatment |
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Related Terms
Bacteria
Bacteria are single-celled prokaryotic microorganisms that lack a membrane-bound nucleus and reproduce primarily by binary fission. They are among the most abundant life forms on Earth, inhabiting nearly every environment including soil, water, and the human body. Bacteria play essential roles in nutrient cycling, decomposition, and digestion, and certain species cause infectious diseases while others are harnessed in biotechnology and food production.
Virus
A virus is an obligate intracellular parasite consisting of genetic material (DNA or RNA) enclosed in a protein coat called a capsid, and sometimes surrounded by a lipid envelope. Viruses cannot reproduce independently; they hijack the cellular machinery of a host cell to replicate. They cause a wide range of diseases in humans, animals, and plants, and are also essential tools in molecular biology and gene therapy research.
Antibiotic
An antibiotic is a chemical substance, originally derived from microorganisms such as fungi or bacteria, that inhibits the growth of or kills bacteria by targeting bacterial-specific structures such as cell walls, ribosomes, or DNA replication machinery. Antibiotics have been among the most important medical discoveries of the 20th century, dramatically reducing mortality from bacterial infections. However, their overuse and misuse have accelerated the emergence of antibiotic-resistant strains, posing a major global health challenge.
From Greek "pathos" (πάθος) meaning "suffering" or "disease" and "genos" (γένος) meaning "producer" or "origin". The word literally means "that which produces disease". The concept was formalised during the germ theory era by Robert Koch and Louis Pasteur in the 1870s–1880s.