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Epidemiology The science of disease - Coggle Diagram
Epidemiology
The science of disease
Branch of public health that studies disease & how it spreads among human & non- human populations.
Goal: control & limit the spread of pathogens & other negative health problems
Epdimologists are often called disease detectives search for disease cause, identify people at risk, how to control or stop spread or prevent it from happening again
Epidemiology triangle: tool that scientists use for addressing the three components that contribute to spread of disease: an external agent, a susceptibility host, and an environment that brings the agent and host together
Between vertices, scientists will often describe the center of triangle as representing time.
Critical to fully assess each component in order to develop effective control & prevention measures
Triangle
What (the agent)
Cause of disease, factors influencing if exposure will result in disease, pathogenicity, & dose
Who (host)
Variety of factors intrinsic to host, ‘risk factors, influence individual’s response to causative agent. Susceptibility affected by genetic composition, nutritional, immunologic status.
Where (environment)
Favorable surroundings & conditions external to host that cause or allow the disease to be transmitted. Physical factors, biological factors, socioeconomic factors.
When (time)
Time may refer to
Incubation period
Duration of illness
Time a person can be sick before death or recovery occurs
Period from infection to the threshold of an epidemic for a population
Chain of infection
Infectious agents
Bacteria, fungi, parasites, viruses
Reservoir
Habitat in which infectious agent normally lives.
Human reservoir
Case: clinical or sub clinical
Carrier: person with no symptoms who is capable of transmitting pathogens to others
According to type
Passive carrier
Active carrier
Incubatory carrier
Convalescent carrier
According to duration
Temporary carrier
Chronic carrier
According to portal exit:
Respiratory carrier eg. Influenza
Fecal carrier (typhoid, dysentery, cholera)
Blood carrier eg. Hepatitis B & AIDS
Urinary or sexual eg. Gonococcus & AIDS
Animal reservoir
Animals or birds (cases or carriers
Infectious disease transmissible under natural conditions from animal to huma (zoo tonic disease
Environmental reservoir
Plants, soil, water in env. Also reservoirs for some infectious agents eg. Tetanus, gas gangrene, anthrax
Portal of exit
Path by which pathogen leaves its host (reservoir)
usually corresponds to site where pathogen is localized
Some blood borne agents can exit by crossing placenta from mother to fetus (toxoplasmosis), through cuts & needles in skin or blood sucking arthropod (malaria)