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Ch 19 Epidemiology

Terms in this set (87)

Epidemiology
Study of disease patterns in populations. "Disease detectives" that collect and compile data about sources of disease and associated risk factors to design infection control strategies and to prevent or predict spread of disease using diverse disciplinarians like ecology, microbiology, sociology, statistics, and psychology.
Contagious or Communicable diseases
Diseases that can be transmitted from one host to another. Transmission is determined by interactions between the environment, pathogen, and host. Control of any of these factors may break the cycle of infection.
Non-communicable diseases
Diseases that do not spread from one host to another. Microorganisms that cause these diseases most often arise form an individuals normal microbiota or from the environment.
Rate of disease in a population
Epidemiologists generally are less concerned with the absolute number of cases of a disease than they are with the rate. Higher rate or proportion of the population infected is of greater concern.
Attack rate
Describes percentage of people who become ill in a population after exposure to an infectious agent. Ex; 100 people at a party eat chicken contaminated with Salmonella, 10 people develop symptoms so attack rate is 10%. This rate reflects many factors including infectious dose of organism and immune status of population.
Incidence
Number of new cases in a specific time period in a given population. Provides a useful measure of the risk of an individual contracting the disease.
Prevalence
Is the total number of cases at any time or for a specific period in a given population. This reflects overall impact of a disease on society because it includes both old and new cases, taking the duration of the disease into account.
Morbidity
Refers to the incidence of disease in a population at risk. Contagious diseases like influenza often have high morbidity rate because each infected individual may transmit the infection to several others.
Mortality
Refers to overall death rate in a population. In developed countries, mortality is most often associated with non-communicable diseases such as cancer or heart attacks. In developing countries, communicable diseases are still a major cause of death.
Case fatality rate
Percentage of population that dies from a specific disease. Disease like plague or Ebola hemorrhagic fever are feared because of their very high cause fatality rate. This rate for AIDS has decreased due to improved treatment, the prevalence of AIDS has increased because more people with the disease survive within the population.
Endemic
Constantly present in a given population ex; common cold is endemic in the US.
Sporadic
When cases occur only from time to time, they are sporadic.
Epidemic
An unusually large number of cases in a population constituents an epidemic. Are causes by diseases not normally present in a population, like cholera being reintroduced to Western Hemisphere, or fluctuations in incidence of endemic diseases like influenza and pneumonia.
Outbreak
Describes a cluster of cases occurring during a brief time interval and affecting a specific population; an outbreak may herald the onset of an epidemic.
Pandemic
When an epidemic spreads worldwide, like AIDS, it is called a pandemic.
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