smittekilde

Smittekilde is a term used in epidemiology and public health to denote the source of infection in a population. It refers to the person, animal, object, or environmental factor from which an infectious agent originates and to which new cases can be traced. Identifying the smittekilde is a central step in outbreak investigation and contact tracing, as it helps define transmission chains and guide control measures.

The word is Danish, composed from smitte (infection) and kilde (source). In practice, the smittekilde may be a primary case (index case), a contaminated item such as a utensil or medical instrument, a contaminated food product, or an environmental reservoir that harbors the pathogen. The actual source may be difficult to determine, and sometimes multiple sources contribute to spread.

In an outbreak, public health teams work to establish the smittekilde through interviews, traceback analyses, and environmental testing. Once identified, interventions target the source and potential routes of transmission to prevent further cases. The term is often used alongside related concepts such as transmission, reservoir, and vector.

See also: index case, outbreak investigation, infection control, infectious disease epidemiology, public health surveillance.

Note: While commonly used in Danish-language literature and clinical settings, the English equivalents include "source of infection" or "source" and "index case."