Epidemiology Triangle



Theepidemiologic triangle describes a model, which has been developed byscientists in an attempt to study health problems. The triangle helpsin understanding infectious diseases and their spread. The trianglecomprises of three vertices, which represents the agent, the host,and the environment (Nelson &amp Williams, 2014). The agent is alsoknown as the “what” of this triangle it indicates the causes ofthe disease. The host vertex is also referred to as the “who” ofthis triangle. It usually indicates the organism that harbors thedisease being studied.

Onthe other hand, the environment vertex indicates the externalfactors, which cause or permit the transmission of the disease. It isalso referred to as the “where” of this triangle. In addition,this triangle comprises of time time indicates the interaction ofthe host, agent and the environment. In some cases, this may be along period while in other cases it may take just a short period(Friis &amp Sellers, 2014). The model represented by theepidemiology triangle is the causation model. This is because itindicates the agent, host and environment leading to a certaininfectious disease.

Anexample relevant to this triangle entails the following:

EpidemiologicTriangle for TB

Agent–this will indicate the organism causing TB mycobacteriumtuberculosis (TB organism)

Environmentconditions that permit the transmission of TB. These will include

– Poorventilation



Hostthe organism harboring the disease will be an organism with

– Concurrentdisease

  • Low immunity

  • Poor nutrition

EpidemiologicTriangle for Malaria

Agent– the agent here is Plasmodium

Host– the host is human

Environment– the external factors leading to the transmission of the diseaseentails

    • Climate

    • Settlement patterns

    • Vector competence

    • Genetics


Friis,R. H., &amp Sellers, T. A. (2014). Epidemiologyfor public health practice.Burlington, Mass: Jones &amp Bartlett Learning.

Nelson,K. E., &amp Williams, C. M. (2014). Infectiousdisease epidemiology: Theory and practice.Burlington, Mass: Jones &amp Bartlett Learning.