Bed bugs (Cimex lectularius and Cimex hemipterus) are obligate blood-feeding ectoparasites that live in close association with humans, yet they are not recognized as vectors of infectious disease. This review synthesizes existing evidence to explain why bed bugs fail to function as disease vectors despite their demonstrated ability to harbor human pathogens under laboratory conditions. A systematic literature search was conducted across multiple stages and was last updated on July 26, 2025, using Scopus, PubMed, and Google Scholar, yielding 21 relevant studies, including experimental investigations of bed bug immunity and theoretical analyses of vector competence. Moreover, after the comparative analysis with other blood-feeding insects, the reviewed literature indicates that bed bugs possess multiple biological and behavioral barriers to transmission, including strong innate immune responses, antimicrobial activity, limited pathogen dissemination beyond the gut, absence of salivary gland involvement, rare defecation on hosts, brief feeding duration, and restricted host switching. While certain pathogens can persist or replicate transiently in bed bugs under experimental conditions, no natural transmission to humans has been documented. This review highlights that bed bug vector incompetence arises from the cumulative effect of these constraints rather than a single limiting factor.
Lim et al. (2026) studied this question.