Epidemiologists study patterns of disease in populations. Before comparing cases or deciding whether a health problem is growing, they must define who is at risk and how disease occurrence will be measured.
A population is the group of individuals at risk for a disease or condition. It may be defined by geography, such as people living in a particular county, or by other characteristics that affect risk. These characteristics might include behaviors, such as intravenous drug use, owning a particular type of pet, or membership in an institution such as a college.
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Prevalence and incidence
Prevalence describes existing cases at a specified time; incidence describes new cases during a specified period.
Morbidity rate
A measure that relates the number of diseased people to a population size.
Mortality rate
A measure of deaths in relation to a defined population.
Etiology and etiologic agent
Etiology concerns the cause of a disease; an etiologic agent is the cause identified as responsible.
Association and causation
An observed association between an exposure and illness does not, by itself, prove that the exposure caused the illness.
Quiz questions
In epidemiology, what makes a disease pattern an epidemic?Answer: More cases than expected in a geographic region over a short period.
What distinguishes a pandemic from an epidemic?Answer: A pandemic is an epidemic occurring on a worldwide scale.
Which sequence best summarizes the traditional criteria in Koch’s postulates?Answer: Associate a microorganism with disease, culture it, reproduce disease in a susceptible host, and recover it.
What do molecular Koch’s postulates help investigators assess?Answer: Whether specific microbial traits or genes contribute to the ability to cause disease.
What is the role of the National Notifiable Disease Surveillance System (NNDSS)?Answer: It supports disease monitoring through cooperation between the CDC and public health partners.
Based on Microbiology by Nina Parker, Mark Schneegurt, Anh-Hue Thi Tu, Philip Lister, Brian M. Forster (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.