Chapter 16- Epidemiology Flashcards
Epidemiology
The study of factors influencing the frequency and distribution of diseases
What do epidemiologists do?
collect, compile data about sources of disease and risk factors
Communicable diseases
Transmitted from one host to another with different degrees of contagiousness (ex. measles, colds, influenza)
Non communicable diseases
do not spread from host to host (ex, legionella pneumophila)
Attack rate
percentage of people who become i’ll in population after exposure to infectious agent
Incidence
number of new cases/time/population
-measure of risk of an individual contracting a disease
prevalence
total number of cases at any time or for a specific period in a given population
morbidity
incidence of disease in a population
Mortality
overall death rate in population
Case-fatality rate
percentage of population that died from a specific disease
Endemic disease
constantly present in population
Sporadic
unusually large number of cases
Outbreak
group of cases at specific time and population
pandemic
global
Fomites
non living objects that facilitate the indirect transmission of pathogens
Chain of infection
Reservoir of infectious agent-portal of exit-transmission-portal of entry-susceptible host
Reservoir of infection
natural habitat of pathogen-living/nonliving, in or on animal, human, or environment
Symptomatic infections
clear source of pathogens, disease may be spread before symptoms appear or after they go away
Asymptomatic infections
harder to identify, carriers may not notice infection, can spread it to others
Portal of exit
body surface or orifice: exit route for pathogen
(ex. intestinal tract (e.coli) respiratory tract, skin, genitalia pathogens)
V. cholerae
intestinal tract organisms exit in the feces, watery diarrhea
S. aureus
shed on skin cells
Vertical transmission
pregnant woman to fetus or mother to infant during childbirth, breast feed
Horizontal transmission
person to person via air, physical contact, ingestion of food or water, or vector
Direct transmission
involves immediate transfer or infectious agent to portal of entry
Direct contact
touch, handshake, sexual intercourse
Vehicle transmission
transmission of pathogens via water, food, air (tainted food)
Indirect transmission
several ways: airborne, vehicle borne(transmitted by objects, food, water), fomites
Mechanical vector (indirect)
carrie’s microbe on its body from one location to another
Biological vector (indirect)
participates in life cycle of pathogen
Vector
living organism that can carry pathogen
Portal of entry
body surface or orifice: entry route for pathogen
Virulence
ability to cause disease
Dose
number of pathogens introduced; minimum number of pathogens required to produce symptoms
incubation period
influences extent of spread
Population characteristics that influence epidemiology of disease
immunity
general health
age
gender
religious practices
genetic background
Descriptive studies
define characteristics of disease outbreak, person/place/time
Analytical studies
more detailed/analyze, determines risk factors relevant to spread of disease
Experimental studies
Trying different treatments, often used to test effectives of a specific treatment
CDC
provides support for infectious disease laboratories in the US
WHO
- Provide worldwide guidance in field of health
- Set global standards for health
- Cooperatively strengthen national health programs
- Develop and transfer appropriate health technology
Reduction/eradication of disease
Reduction through sanitation, vector control, vaccination, abx
(ex. smallpox, measles, polio)
Emerging disease
novel or have recently increased in incidence (ex. covid, ebola)
Factors that contribute to emergence/reemergence
Microbial evolution
Complacency
Behavioral changes
Technology
Population expansion
Development
Food distribution and importation
War and civil unrest
Climate changes
HAI’s (Healthcare associates infections)
acquired while receiving treatment in a healthcare setting (ex. C. diff, E. coli, Pseudomonas, S.aureus, surgical site infections, GI infections)
HAI transmission
other patients, healthcare environment, workers, visitors, medical devices
