epidemie

An epidemic is the rapid spread of an infectious disease beyond what is normally expected in a specific community or region within a defined period. It implies higher-than-expected incidence.

Epidemics occur when a pathogen enters a population with enough susceptible people. Factors include crowding, mobility, waning immunity, and environmental conditions. Transmission can occur by contact, droplets, vectors, or contaminated food. The scale of an epidemic depends on the pathogen's basic reproduction number, R0, and on interventions that limit spread.

An outbreak is an epidemic that is limited in place or time; an endemic disease is regularly found in a population at a stable level. When a disease spreads across large regions or continents, it is called a pandemic.

Surveillance, laboratory testing, and epidemiological investigation detect epidemics. Public health measures track cases, identify contacts, and implement controls to interrupt transmission.

Responses include case management, vaccination campaigns when available, isolation and quarantine, travel advisories, hygiene improvements, and community engagement. Social and economic considerations influence effectiveness.

Historical examples include the 1918 influenza pandemic, West Africa Ebola outbreaks, and seasonal influenza epidemics. Ongoing risks from emerging pathogens and antimicrobial resistance require robust health systems and international cooperation.