While household transmission of C diff infection is low, there was increased incidence after a familial exposure.
Investigators from the University of Iowa conducted a case-control study of 224,828 infections in order to determine if the incidence of C diff infection was greater among individuals surrounded by those with a previous exposure. This type of transmission has been studied in smaller investigations, but the study authors used a database of longitudinal insurance claims to collect data from 194,424 insurance plan enrollees between 2001 and 2017.
Cases of C diff were included in the analysis when there were households of 2 or more family members on the same insurance plan for an entire month, the study authors said. There was no distinction made between health care-associated and community-acquired cases.
The mean age of patients with C diff was 52 years and about half of them were female. The study authors determined that 40% of cases were hospital-associated — or diagnosed during an inpatient hospitalization – while the remainder were community onset. The investigators said that community onset cases were attributed to either community or hospital exposure to C diff. Cases of the infection tended to occur in older patients, more frequently female patients, and smaller households, such as those with only 2 family members.
However, the study authors said, cases of C diff that represented possibly transmission more often occurred in patients aged between 0 and 17 years and in households of a larger size, such as 4 or more people. Not only was prior family exposure increased with increased incident of C diff infection, the study authors said, but that rate represented the covariate with the second highest incidence rate ratio after prior hospital exposure.
Additionally, the investigators determined that family exposure was still linked to greater incidence of hospital-onset C diff infection. Estimated association for prior family exposure of C diff was decreased among family members aged 18 to 26 years, the study authors added.
Overall, the study authors found that there was a 21 times greater incidence among individuals with family exposure compared to nonexposed individuals. This was true even after controlling for C diff infection risk factors and different model specifications, the study authors wrote.
“These results suggest that individuals with family exposure may be at greater risk for acquiring C diff infection than those without exposure and highlight the importance of the shared environment in the transmission and acquisition of C diff,” the study authors wrote. “While our results show a relatively high degree of association between family exposure and C diff infection, the level of risk attributable to household C diff infection transmission remains low.”
The study authors did note, however, that approximately 0.48% of all C diff infection cases could potentially be attributable to family exposure. From their findings, the investigators are able to suggest that family exposure followed by diarrhea could benefit from testing for C diff infection.
“Although the absolute risk of C diff infection following family exposure is low compared with other established risk factors, family exposure confers a high degree of relative risk,” the study authors wrote. “Thus, our results may have implications for highlighting the role of the environment in the spread of C diff infection as well as practical implications for preventing the spread of C diff infection in the household setting.”