EPIDEMIOLOGY

Epidemiology

The study of the frequency and distribution of disease and contributing factors.

Morbidity Rate

The number of new cases of a particular disease that occurred during a specified period per a specified defined population.

Incidence

The number of new cases of a particular disease in a defined population over a specific period.

Endemic Disease

A disease that is always present within a population in a particular geographic area, with case numbers fluctuating but never dying out completely.

Epidemic Disease

A greater than usual number of cases of a disease in a particular region, usually occurring within a relatively short period and involving a large number of people.

Pandemic Disease

A disease occurring in epidemic properties across many countries simultaneously.

Sporadic Disease

A disease that occurs only occasionally within the population of a specific geographic area.

Zoonotic Disease

An infectious disease that humans acquire from an animal source.

Communicable Disease

An infectious disease that is transmissible from one human to another.

Contagious Disease

A communicable disease that is easily transmitted from one person to another.

Chain of Infection

The sequence involving etiologic agent, reservoir, portal of exit, method of transmission, portal of entry, and susceptible host necessary for disease transmission.

Six Components of Infectious Disease

Pathogen, source of the pathogen, portal of exit, mode of transmission, portal of entry, and susceptible host.

Direct Transmission

Transmission that occurs through direct contact, such as skin-to-skin contact, handshaking, kissing, or sexual intercourse.

Indirect Transmission

Transmission involving contamination of food, water, vectors, or fomites that have been contaminated.

Common Routes of Transmission

Methods of transmission for infectious diseases, including skin, respiratory, salivary, gastrointestinal, genital secretion, and blood.

Reservoir

The site where a pathogen can multiply or survive until transferred to a host; it can be living (humans, animals) or non-living (air, soil).

Passive Carrier

A carrier that transports the pathogen without ever having had the disease.

Incubatory Carrier

A person who can transmit a pathogen during the incubation period.

Convalescent Carrier

A person who can transmit a pathogen while recovering from a disease.

Active Carrier

A person who has completely recovered from a disease but continues to harbor the pathogen indefinitely.