epidemics vocab

Communicable disease

Disease that can be transmitted from one host to another

Noncommunicable disease

Disease not spread from host to host; usually environmental, genetic, or from normal microbiota

Notifiable disease

Disease required by law to be reported to health authorities for monitoring

Epidemic

A sudden increase in disease cases above normal levels in a population

Common source epidemic

Many people infected from one shared source (e.g., contaminated water)

Propagated epidemic

Disease spreads person-to-person over time

Index case

First identified case in an outbreak

R0 (Basic reproduction number)

Number of people one infected person will pass the disease to on average

Endemic

Disease occurs at a constant, predictable rate in a population

Pandemic

Worldwide epidemic affecting multiple countries or continents

Sporadic

Disease occurs only occasionally in low numbers

Incidence rate

Number of new cases in a population during a defined time period

Prevalence rate

Total number of existing cases at one point in time

Virulence factor

Microbial trait that allows infection or damage to host tissues

Opportunistic pathogen

Causes disease only when host defenses are weakened

Reservoir

Where the pathogen normally lives and multiplies

Zoonosis

Disease that spreads from animals to humans

Infectious dose

Number of microbes needed to establish infection in a host

Portal of entry

Where pathogens enter a new host (e.g., respiratory tract, mucous membranes)

Portal of exit

Route pathogens leave the host (e.g., droplets, blood, feces)

Direct contact

Transmission through physical contact with infected host

Droplet transmission

Transmission via respiratory droplets traveling short distances

Vertical transmission

Transmission from mother to fetus or newborn

Fomite

Nonliving object that spreads pathogens

Vehicle

Food, water, or blood that can carry pathogens and allow them to multiply

Vector

Living organism (often an arthropod) that transmits pathogens

Biological vector

Pathogen reproduces inside the vector

Mechanical vector

Vector physically carries pathogen on surface

Healthcare-associated infection (HAI)

Infection acquired while receiving medical care

Herd immunity

When enough people are immune to a disease, reducing spread and protecting susceptible individuals