Infektiv

Infektiv is a term used in epidemiology and microbiology to describe the ability of a pathogen to establish an infection in a susceptible host. In English-language literature, the corresponding term is infectivity or infective potential. It is an aspect of transmissibility that focuses on the initial stages of infection rather than the severity of disease (virulence) or the ease with which an infected person transmits the pathogen to others (contagiousness). Infectivity depends on both pathogen factors—such as receptor binding, entry mechanisms, stability in the environment, and the infectious dose required to cause infection—and host factors, including immune status and genetic susceptibility. Environmental conditions and the route of transmission also influence observed infectivity, because different pathogens are more likely to initiate infection via respiratory droplets, aerosols, fecal-oral routes, bloodborne exposure, or vectors.

Infectivity is often quantified indirectly by measures such as the infectious dose (ID50) needed to establish infection in 50% of exposed individuals, or by parameters contributing to the basic reproduction number R0. High infectivity means a pathogen can establish infection at a lower exposure dose or with a higher probability. Public health strategies aim to reduce effective infectivity by reducing exposure, improving host immunity, or interrupting transmission routes (hand hygiene, vaccination, ventilation, isolation).

Infektiv is commonly contrasted with virulence, which describes disease severity, and with contagiousness, which describes ease of spread.