overwintering

In epidemiology, the term "overwintering" describes the process whereby vector-borne pathogens survive in cold seasons while their hosts hibernate or are otherwise dormant. This enables many dangerous pathogens—such as viruses that cause dengue and encephalitis, rickettsial species, and malaria parasites—to become active and invade new susceptible hosts when warmer weather returns. The risk of epidemic spread of a vector-borne pathogen during the hot (or wet) season commonly depends more on the successful overwintering of the pathogen during the cool, dry season than on an introduction of fresh pathogens from elsewhere.

(SEE ALSO: Pathogenic Organisms; Vector-Borne Diseases)

— JOHN M. LAST

The persistence of an infectious agent in its vector for an extended period, as in the cooler winter months, during which the vector has no opportunity to be reinfected or to infect another host.