The time or times during which the infectious agent may be transferred directly or indirectlyfrom an infected person to another person, from an infected animal to human, or from an infected human to an animal, including arthropods. In diseases such as diphtheria and scarlet fever, in which mucous membranes are involved from the first entry of the pathogen, the period of communicability is from the date of first exposure to a source of infection until the infective microorganism is no longer disseminated from the involved mucous membranes, ie, from the period before the prodromata until termination of a carrier stage, if this develops. Most diseases are not communicable during the earlyincubation period or after full recovery. In diseases transmitted by arthropods, such as malaria and yellow fever, the periods of communicability are those during which the infectious agent occurs in infective form in the blood or other tissues of the infected person in sufficient numbers to permit vector infections. A period of communicability is also to be distinguished for the arthropod vector – namely, that time during which the agent is present in the tissues of the arthropod in such form and locus (infective stage) as to be transmissible.
Article Categories:Dictionary of Tropical Medicine