Britannica
Sources used in this answer
- human disease - Classifications of diseases
- infectious disease - The inanimate environment
- biological weapon - Biological warfare agents
- Plant disease - Infectious disease-causing agents
- human disease - Diseases of nutritional excess
- human disease - Diseases of nutrition
- epidemiology - Epidemiological models
- Plant disease - Diseases caused by bacteria
- human disease - Infectious agents
- human disease - Chemical injury: poisoning
- epidemiology
What kinds of biological, chemical, nutritional, and physical agents can cause disease?
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epidemiology
Researchers using genomic information to trace the transmission routes in past epidemics of plague.
In the field of epidemiology, the occurrence of disease is often analyzed using the "epidemiologic triad," which balances factors related to the host, the environment, and the disease-causing agent. Agents are the specific factors that cause disease and are categorized as follows:1
- Biological Agents: These include living organisms such as bacteria, fungi, viruses, rickettsiae, and various parasites.213
- Chemical Agents: These encompass a wide range of natural or synthetic compounds, including gases, poisons, and drugs. Chemical injury occurs when these substances interfere with cellular homeostasis or are ingested in toxic quantities.14
- Nutritional Agents: These relate to the intake of nutrients, where both deficiencies and excesses can lead to disease. Examples include food additives or the excessive consumption of vitamins and caloric intake, which can contribute to conditions like obesity and atherosclerosis.51
- Physical Agents: These include external factors such as ionizing radiation and other environmental stressors that can cause physical injury or disease.1