Principles of Disease and Epidemiology

Vocabulary practice flashcards covering core concepts, pathogen-host relationships, disease patterns, transmission mechanisms, and epidemiology based on Chapter 14 of Tortora, Funke, and Case's Microbiology.

Pathology

The scientific study of disease, which includes the investigation of etiology, pathogenesis, and structural and functional changes in the body.

Etiology

The study of the cause or origin of a disease.

Pathogenesis

The manner in which a disease develops within a host.

Infection

The invasion or colonization of the body by pathogenic microorganisms.

Disease

An abnormal state in which the body is not functioning normally, resulting in structural and functional alterations.

Normal Microbiota

Microorganisms that establish permanent residence in and on the body without producing disease under normal conditions.

Transient Microbiota

Microorganisms that may be present on or in the human body for days, weeks, or months and then disappear.

Commensalism

A symbiotic relationship in which one organism benefits while the other organism is unaffected.

Mutualism

A type of symbiosis that benefits both organisms involved.

Parasitism

A symbiotic relationship in which one organism benefits at the expense of the other by deriving nutrients from the host.

Opportunistic Pathogens

Microorganisms that do not cause disease in their normal habitat in a healthy individual, but can do so in a different environment or when the host defenses are weakened.

Microbial Antagonism

The competitive exclusion mechanism by which normal microbiota protect the host by competing for niches, altering pH, and producing substances such as bacteriocins.

Probiotics

Live microbial cultures applied to or ingested into the body that are intended to exert a beneficial physiological effect.

Human Virome

The viral component of the human microbiome, consisting primarily of bacteriophages as well as persistent and latent viruses inhabiting body surfaces.

Koch's Postulates

A four-step experimental framework used to establish a causal relationship between a specific causative microbe and a specific infectious disease.

Symptom

A subjective change in body function felt by a patient as a result of a disease, such as pain or malaise.

Sign

An objective, observable change in the body that can be directly measured or evaluated by a healthcare provider, such as fever, edema, or lesions.

Syndrome

A specific group of signs and symptoms that consistently accompany and characterize a particular disease.

Communicable Disease

Any disease that spreads from one host to another, either directly or indirectly.

Contagious Disease

A communicable disease that is capable of spreading easily and rapidly from one person to another.

Noncommunicable Disease

A disease that is not transmitted from one host to another, caused by environmental microbes or opportunistic resident microbiota.

Incidence

The fraction or proportion of a population that contracts a disease during a specific time period; reflects new cases.

Prevalence

The total fraction of a population exhibiting a specific disease at a given time, encompassing both old and newly identified cases.

Sporadic Disease

A disease that occurs only occasionally in an irregular manner within a population.

Endemic Disease

A disease that is constantly present at a steady, baseline level within a particular geographic region or population.

Epidemic Disease

A disease acquired by a large number of hosts in a given area within a relatively short period of time.

Pandemic Disease

An epidemic disease that has spread worldwide across multiple countries or continents.

Herd Immunity

Resistance to the spread of an infectious disease within a population that results when a sufficiently high proportion of individuals have acquired immunity.

Acute Disease

A disease characterized by rapid onset of symptoms that lasts only a relatively short duration.

Chronic Disease

A disease that develops slowly, produces less severe initial symptoms, and persists or recurs for extended periods.

Subacute Disease

A disease with an intermediate pattern of duration and severity between an acute disease and a chronic disease.

Latent Disease

A disease condition in which the causative pathogen remains inactive or dormant for an extended period without causing symptoms, later reactivating to produce illness.

Local Infection

An infection in which pathogenic microorganisms are confined to a relatively small, specific region of the body.

Systemic Infection

A generalized infection throughout the body resulting from the dissemination of microbes or their products through blood or lymph.

Focal Infection

A systemic infection that originates as a localized focus of infection in areas such as teeth, tonsils, or sinuses.

Sepsis

A toxic inflammatory condition arising from the spread of microorganisms or their toxins from a focus of infection.

Bacteremia

The presence of bacteria circulating within the bloodstream.

Septicemia

A systemic disease caused by the active growth and multiplication of pathogenic bacteria within the bloodstream.

Toxemia

The presence of microbial toxins in the blood.

Viremia

The presence of viruses in the bloodstream.

Primary Infection

An acute infection that causes the initial illness in a previously healthy host.

Secondary Infection

An opportunistic infection caused by pathogens taking advantage of a host whose defenses were weakened by a primary infection.

Subclinical Disease

An inapparent infection that does not produce any noticeable signs or symptoms in the infected host.

Predisposing Factor

Any underlying biological, environmental, or lifestyle condition that makes the host more susceptible to developing a disease.

Incubation Period

The time interval between the initial infection and the earliest appearance of any clinical signs or symptoms.

Prodromal Period

A brief stage following the incubation period characterized by early, mild, and nonspecific symptoms such as general malaise.

Period of Illness

The phase of an infectious disease where signs and symptoms reach their peak severity and overt indicators of disease are present.

Period of Decline

The stage of disease during which the signs and symptoms subside, leaving the patient temporarily vulnerable to secondary infections.

Period of Convalescence

The final recovery phase of an infectious disease during which the patient regains strength and normal body functions are restored.

Reservoir of Infection

A continual living or nonliving ecological source that provides a pathogen with the necessary conditions for survival, multiplication, and transmission.

Zoonosis

An infectious disease that occurs primarily in wild or domestic animals and can be transmitted to humans.

Carriers

Individuals who harbor pathogenic microbes and transmit them to susceptible individuals without displaying any noticeable signs of disease.

Fomite

Any nonliving object involved in the indirect contact transmission of an infectious pathogen.

Droplet Transmission

Contact transmission of infectious pathogens via mucus droplets discharged into the air by coughing or sneezing that travel distances of less than $1\,\text{meter}$.

Vehicle Transmission

The spread of disease agents through inanimate media such as contaminated water, food, or air.

Mechanical Transmission

The passive transport of infectious pathogens on the exterior body parts or feet of an arthropod vector without the pathogen replicating internally.

Biological Transmission

An active transmission process where an arthropod vector ingests a pathogen that subsequently multiplies or undergoes life cycle development within the vector prior to transmission.

Nosocomial Infection

A healthcare-associated infection (HAI) acquired during a stay or treatment in a healthcare facility that was neither present nor incubating at admission.

Compromised Host

An individual whose immune defenses or physical barriers have been impaired by disease, therapy, burns, or wounds, elevating vulnerability to infection.

Emerging Infectious Diseases (EIDs)

Infectious diseases that are newly appearing in a population, increasing in incidence, or showing potential to expand geographically in the near future.

Epidemiology

The branch of medicine and public health that studies when and where diseases occur and how they are transmitted within human populations.

Descriptive Epidemiology

The collection and retrospective evaluation of all relevant epidemiological data outlining the occurrence and distribution of a disease.

Analytical Epidemiology

An epidemiological method that compares a diseased population against an unaffected control group to identify the probable cause of the condition.

Experimental Epidemiology

The testing of a disease hypothesis through prospective, controlled experiments or randomized trials.

Morbidity

The incidence or number of individuals affected by a specific notifiable disease within a population during a defined period.

Mortality

The number of deaths caused by a specific disease in a population over a given time interval.