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the scientific study of disease


the study of the cause of disease


the manner in which a disease develops


the invasion or colonization of the body by pathogenic microorganisms


occurs when an infection results in any change from a state of health

normal microbiota (normal flora)

microorganisms that live in the body and do not produce disease under normal conditions

transient microbiota

may be present in the body for several days, weeks, or months then disappear

microbial antagonism or competitive exclusion

normal microbiota benefit the host by preventing the overgrowth of harmful microorganisms


a type of symbiosis where one of the organisms benefits and the other is unaffected


a relationship between two organisms in which at least one organism is dependent on the other


a type of symbiosis that benefits both organisms


live microbial cultures applied to or ingested that are intended to exert a beneficial effect


a type of symbiosis where one organism benefits by deriving nutrients at the expense of the other organsim

opportunistic pathogens

microorganisms that ordinarily do not cause disease in their normal habitat in a healthy person, but may do so in a different environment (e. coli)

infectious diseases

diseases caused by microorganisms

Koch's postulates

used to determine the etiology of a disease


changes in body function that is felt by a patient as a result of disease


objective changes that can be observed and measured as a result of disease


a specific groups of signs or symptoms that always accompany a particular disease

communicable disease

any disease that spreads from one host to another either directly or indirectly

contagious disease

diseases that are easily spread from one person to another

noncommunicable disease

a disease that is not spread from one host to another


the number of people in a population who develop a disease during a particular time period


the number of people in a population who develop a disease at a specified time regardless of when it first appeared

sporadic disease

diseases that occur only occasionally in a pnopulatio


a disease constantly present in a population


many people in a given area acquire a certain disease in a relatively short period


an epidemic disease that occurs worldwide

acute disease

a disease that develops rapidly but lasts only a short time

chronic disease

a disease that develops more slowly and the body's reactions may be less severe, but it is likely to continue or recur for long periods

subacute disease

a disease that is intermediate between acute and chronic

latent disease

a disease in which the causative agent remains inactive for a time, but then becomes active to produce symptoms of the disease

herd immunity

when many immune people are present in a community

local infection

an infection in which the invading microorganisms are limited to a relatively small area of the body

systemic (generalized) infection

microorganisms or their products are spread throughout the body by the blood or lymph

focal infection

agents of a local infection enter a blood or lymphatic vessel and spread to other specific parts of the body where they are confined to specific areas of the body


a toxic inflammatory condition arising from the spread of microbes from a focus of infection


blood poisoning, a systematic infection arising from the multiplication of pathogens in the blood


the presence of bacteria in the blood


the presence of toxins in the blood


the presence of viruses in the blood

primary infection

an acute infection that causes initial illness

secondary infection

caused by an opportunistic pathogen after the primary infection has weakened the bodies defenses

subclinical (inapparent) infection

an infection that does not cause any noticeable illness

predisposing factor

makes the body more susceptible to a disease and may alter the course of the disease

incubation period

the interval between the initial infection and the first appearance of any signs or symptoms

prodromal period

a relatively short period that follows the period of incubation in some diseases, early mild symptoms

period of illness

the period the disease is most severe

period of decline

the period the signs and symptoms subside

period of convalescence

the period the person regains strength and the body returns to its prediseased state

reservoir of infection

a continual source of the disease organisms


people who are living reservoirs of infection who do not show signs or symptoms


diseases that occur primarily in wild and domestic animals and can be transmitted to humans

soil and water

two major nonliving reservoirs of infectious disease

contact transmission

the spread of an agent of disease by direct contact, indirect contact, or droplet transmission

direct contact transmission

the direct transmission of an agent by physical contact between its source and a susceptible host

indirect contact transmission

occurs when the agent of disease is transmitted from its reservoir to a susceptible host by means of a nonliving object


the general term for any nonliving object involved in the spread of an infection

droplet transmission

microbes are spread in droplet nuclei that travel only short distances

vehicle transmission

transmission of disease agents by a medium such as food, water, or air


animals that carry pathogens from one host to another

mechanical transmission

the passive transport of the pathogens on the insect's feet or other body parts

biological transmission

an active process of transmission through the blood, pathogen reproduces in the vector

nosocomial infection

infection that does not show any evidence of being present or incubating at the time of admission to a hospital; acquired as a result of a hospital stay

compromised host

host whos resistance to infection is impared by disease, therapy, or burns

emerging infectious diseases

diseases that are new or changing, showing increase in incidence in the recent past


the science that studies when and where diseases occur and how they are transmitted in populations

descriptive epidemiology

entails collecting all data that describe the occurrence of the disease under study

analytical epidemiology

analyzes a particular disease to determine its probable cause

experimental epidemiology

begins with a hypothesis about a particular disease and experiments to test the hypothesis


a branch of the U.S. Public Health Service located in Atlanta, GA.


the incidence of specific notifiable diseases


the number of deaths from specific diseases

morbidity rate

the number of people affected by a disease in a population in a given period of time

mortality rate

the number of deaths resulting from a disease in a population in a given period of time

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