Chapter 16- Disease and epidemiology Flashcards
Epidemiology
The study of factors and mechanisms that are involved in the frequency and spread of diseases which affect humans, plants, and animals. When studying a disease, the first task of an epidemiologist is to determine the cause of disease- the etiologic agent. The goal is to obtain information useful in preventing the spread of disease. Methods used are descriptive, analytical, and experimental
Epidemiologic analysis is always carried out in regards to
Reference to the risk population. Susceptible individuals can be defined by behaviors (IV drug use, etc)
Morbidity rate
indicates the number of cases as a percentage of the population
Mortality rate
the measure of deaths in the population- the number per one hundred thousand people
Prevalence rate
Number of people infected at any one time- the number of people who have a given disease. Expressed in numbers per 100,000 people per year or as percent of the population
Incidence rate
New cases per unit population per unit time period. Expressed in numbers per 100,000 people per year or as percent of the population
How are incidence and prevalence rates related?
Every new case in the incidence rate adds to the prevalence, so prevalence will keep increasing even as incidence is decreasing. Prevalence will only decrease once incidence is basically nonexistent
Sporadic diseases
only seen occasionally and a random and unpredictable manner
Endemic diseases
constantly present is the population
Epidemic diseases
Larger than expected number of cases in a short period of time. You can have an endemic disease that becomes an epidemic due to additional cases. Occurs when you suddenly have a high peak in a graph
Pandemic diseases
Worldwide epidemic. COVID, HIV, smallpox
Propagated epidemics
person to person spread. Spread of disease can occur due to environmental conditions
John Snow
First epidemiological study- John Snow and the water pump on Broad Street. Attempted to determine where everyone who had been infected with cholera was getting their water from, and tracked the cholera outbreak to one contaminated water pump. His work supported the germ theory of disease
Common source
single source for all of the individuals infected
Point source
common source operates for a short period of time
Continuous common source spread
the infection occurs for an extended period of time
Intermittent common source spread
infections occur for a period, stop, and then begin again
Common source related spread of disease (4)
- Common source
- Point source
- Continuous common source
- Intermittent common source
With common source outbreaks, the cases quickly peak. Once the source is determined and removed, the cases quickly decline. The plateau period is very short
Propagated spread
Direct or indirect person to person contact. There is no single source of infection- each infected individual becomes a source for one or more subsequent infections. Difficult to stop and cause longer outbreaks. With propagated outbreaks, the number of cases rises and falls very slowly. There is a long plateau period. The only way to stop the outbreak would be to isolate everyone with the pathogen, but this is typically impossible due to incubation periods
Propagated spread
Direct or indirect person to person contact. There is no single source of infection- each infected individual becomes a source for one or more subsequent infections. Difficult to stop and cause longer outbreaks. With propagated outbreaks, the number of cases rises and falls very slowly. There is a long plateau period. The only way to stop the outbreak would be to isolate everyone with the pathogen, but this is typically impossible due to incubation periods
Observational studies
Data are gathered from study participants through measurements. Methods and types of studies include descriptive epidemiology, analytical epidemiology, retrospective studies, prospective studies, case control studies, and cross sectional studies
Descriptive epidemiology
Gathers information about the disease outbreak and the infected individuals, how the disease spreads over time. Involves examination of samples and medical records and interviewing patients and their families