infeknosti

Infekčnost, commonly translated as infectiousness or infectivity in epidemiology, refers to the capacity of a pathogen to establish infection in a host and to be transmitted to susceptible individuals. It is distinct from virulence (disease severity) and from pathogenicity (ability to cause disease). Infectiousness describes how easily an infected person or organism can spread the pathogen, and can vary over the course of infection and between individuals.

Determinants include properties of the pathogen (surface proteins that enable attachment, replication rate), host factors (immune status, receptor availability), and environmental and behavioral conditions (crowding, ventilation, hygiene). Transmission modes—airborne, droplet, direct contact, fecal-oral, vector-borne—also influence observed infectiousness. Some diseases show high infectiousness before symptoms or during mild illness, complicating control.

Measurement uses metrics such as the basic reproduction number R0, the effective reproduction number Rt, the serial interval, and the secondary attack rate. Infectious period—the time during which an infected person can transmit—is a key component. Viral load and shedding correlate with infectiousness in many infections.

Public health measures to reduce infectiousness include vaccination, which can prevent infection and reduce onward transmission; antiviral or antibiotic treatment; isolation and contact tracing; hand hygiene, respiratory etiquette, masks, ventilation, and crowd avoidance. Surveillance and rapid testing help identify highly infectious cases early.