Title: Modelling diverse sources of Clostridium difficile in the community: importance of animals, infants and asymptomatic carriers,
Abstract: Clostridium difficile infections (CDIs) affect patients in hospitals and in
the community, but the relative importance of transmission in each setting is
unknown. We developed a mathematical model of C. difficile transmission in a
hospital and surrounding community that included infants, adults, and
transmission from animal reservoirs. We assessed the role of these transmission
routes in maintaining disease and evaluated the recommended classification
system for hospital and community-acquired CDIs. The reproduction number in the
hospital was <1 (range: 0.16-0.46) for all scenarios. Outside the hospital, the
reproduction number was >1 for nearly all scenarios without transmission from
animal reservoirs (range: 1.0-1.34). However, the reproduction number for the
human population was <1 if a minority (>3.5-26.0%) of human exposures
originated from animal reservoirs. Symptomatic adults accounted for <10%
transmission in the community. Under conservative assumptions, infants
accounted for 17% of community transmission. An estimated 33-40% of
community-acquired cases were reported but 28-39% of these reported cases were
misclassified as hospital-acquired by recommended definitions. Transmission
could be plausibly sustained by asymptomatically colonized adults and infants
in the community or exposure to animal reservoirs, but not hospital
transmission alone. Underreporting of community-onset cases and systematic
misclassification underplays the role of community transmission.