Epidemiology Review – Key Vocabulary

Vocabulary flashcards covering fundamental epidemiology terms, transmission routes, disease measures, and infection control concepts.

Epidemiology

The study of the distribution and causes of disease in populations.

Communicable (contagious) disease

An illness that can be transmitted from one host to another.

Non-communicable disease

An illness that does not spread from host to host.

Attack rate

Percentage of exposed people who become ill; reflects infectious dose and population immunity.

Incidence

Number of new cases in a population over a specific time period; measures risk of contracting a disease.

Prevalence

Total number of existing cases (old and new) in a population during a time period; shows overall disease impact.

Mortality rate

Percentage of an entire population that dies from a specific disease.

Case-fatality rate

Percentage of individuals with the disease who die from it.

Endemic disease

Disease constantly present in a population at low or controllable levels (e.g., common cold).

Sporadic disease

Disease that appears only occasionally and at irregular intervals (e.g., tetanus).

Epidemic

Unusually large number of cases of an endemic or introduced disease in a region.

Outbreak

A cluster of disease cases occurring in a specific time and population.

Pandemic

A global epidemic (e.g., COVID-19).

Chain of infection

Series of steps by which a pathogen moves from reservoir to susceptible host.

Reservoir of infection

Natural habitat where a pathogen lives and multiplies.

Zoonoses

Diseases that primarily exist in animals but can be transmitted to humans.

Portal of exit

The route by which a pathogen leaves its reservoir or host body.

Vertical transmission

Disease spread from mother to fetus or newborn.

Horizontal transmission

Disease spread between individuals other than mother-to-child.

Direct transmission

Immediate transfer of a pathogen via physical contact, such as handshakes, hugs, or sexual activity.

Indirect transmission

Transfer of a pathogen via an intermediate object or medium.

Droplet nuclei

Microscopic airborne particles that carry pathogens; require N95-level protection.

Airborne transmission

Spread of pathogens through inhalation of droplet nuclei or dust particles.

Vehicle-borne transmission

Spread of pathogens via contaminated inanimate materials (food, water, air, or fomites).

Fomite

Any inanimate object that can harbor and transmit pathogens (e.g., phone, doorknob).

Vector-borne transmission

Spread of disease via living organisms such as arthropods.

Mechanical vector

Vector that carries pathogens on its exterior body surface without being infected.

Biological vector

Vector in which the pathogen multiplies or develops before transmission.

Portal of entry

Body surface or orifice through which a pathogen enters a host.

Fecal-oral transmission

Ingestion of pathogens from fecally contaminated materials.

Virulence

Degree of pathogenicity; ability to cause disease.

Virulence factors

Molecules that enable a pathogen to attach, evade immunity, and damage host tissue.

Infectious dose

Minimum number of pathogens needed to establish an infection.

Incubation period

Time between pathogen entry and onset of symptoms; influences disease spread.

Healthcare-associated infections (HAIs) / Nosocomial infections

Infections acquired while receiving treatment in healthcare settings.