Chapter 59: Principles of Epidemiology Flashcards
what is epidemiology
science that evaluates occurrence, determinants, distribution and control of health and disease in a defined human population
what is sporadic disease and give example
- occurs occasionally and at irregular intervals
- histoplasmosis
- gas gangrene
what is endemic disease and give examples
- maintains a relatively steady low level frequency at a moderately regular interval
- gonorrhea
- dengue fever
what is holoendemic diseases and what is an example
- occurs at a high, constant level throughout a population
- malaria
what is epidemic and give exmaple
- sudden increase in frequency above expected number
- influenza and meningococcal infection
what is the first case in an epidemic called
index case
what is an outbreak
sudden unexpected occurrence of disease
- usually focal or in a limited segment of population
what is a pandemic
increase in disease occurrence within large population over wide region
what is morbidity rate
- an incidence rate
- number of new cases in a specific time period per unit of population
what is prevalance rate
- total number of individuals infected at any one time per unit of population
- depends both on incidence rate and duration of illness
what is mortality rate
number of deaths from a disease per number of cases of the disease
what is R0 or R naught
number of secondary cases one case would produce in a completely susceptible population
R(0) calculated as a function of 3 primary parameters
- duration of contagiousness after a person becomes infection
- likelihood of infection per contact between a susceptible person and an infectious person or vector
- contact rate
what does infectious disease epidemioogy try to determine
- causative agent
- source and/or resevoir of disease agent
- mechanism of transmission
- host and environmental factors that facilitate development of disease within a defined population
- best control measures
what are signs
objective changes in body that can be directly observed
what are symptoms
subjective changes experienced by patient
what is the course of infectious disease
-incubation period
- prodromal stage
- period of illness
- convalescence
what is the incubation period
period after pathogen entry but before signs and symptoms appear
what is prodromal stage
onset of signs and symptoms
- not clear enough for diagnosis
what is period of illness
disease is most severe and has characterisitc signs and symptoms
what is convalescence
signs and symptoms begin to disappear
what are the 2 types of epidemics
common source epidemics and propagated epidemic
what is threshold density
minimum number of individuals necessary to continue propagating the disease
what is herd immunity
resistance of a population to infection and to spread of an infectious organism because of the immunity of a large percentage of the population
