Acute hepatitis B virus (HBV) infections have been reported in long-term care facilities (LTCFs), primarily associated with infection control breaks during assisted blood glucose monitoring. We investigated HBV outbreaks that occurred in separate skilled nursing facilities (SNFs) to determine factors associated with transmission.

Outbreak investigation with case-control studies.

Two SNFs (facilities A and B) in Durham, North Carolina, during 2009–2010.

Residents with acute HBV infection and controls randomly selected from HBV-susceptible residents during the outbreak period.

After initial cases were identified, screening was offered to all residents, with repeat testing 3 months later for HBV-susceptible residents. Molecular testing was performed to assess viral relatedness. Infection control practices were observed. Case-control studies were conducted to evaluate associations between exposures and acute HBV infection in each facility.

Six acute HBV cases were identified in each SNF. Viral phylogenetic analysis revealed a high degree of HBV relatedness within, but not between, facilities. No evaluated exposures were significantly associated with acute HBV infection in facility A; those associated with infection in facility B (all odds ratios >20) included injections, hospital or emergency room visits, and daily blood glucose monitoring. Observations revealed absence of trained infection control staff at facility A and suboptimal hand hygiene practices during blood glucose monitoring and insulin injections at facility B.

These outbreaks underscore the vulnerability of LTCF residents to acute HBV infection, the importance of surveillance and prompt investigation of incident cases, and the need for improved infection control education to prevent transmission.

To determine the timing of community-onset Clostridium difficile–associated disease (CDAD) relative to the patient's last healthcare facility discharge, the association of postdischarge cases with healthcare facility–onset cases, and the influence of postdischarge cases on overall rates and interhospital comparison of rates of CDAD.

Retrospective cohort study for the period January 1, 2005, through December 31, 2005.

Catchment areas of 6 acute care hospitals in North Carolina.

We reviewed medical and laboratory records to determine the date of symptom onset, the dates of hospitalization, and stool C. difficile toxin assay results for patients with CDAD who had diarrhea and positive toxin–assay results. Cases were classified as healthcare facility–onset if they were diagnosed more than 48 hours after admission. Cases were defined as community-onset if they were diagnosed in the community or within 48 hours after admission, and were also classified on the basis of the time since the last discharge: if within 4 weeks, community-onset, healthcare facility–associated (CO-HCFA); if 4-12 weeks, indeterminate exposure; and if more than 12 weeks, community-associated. Pearson's correlation coefficient was used to assess the association between monthly rates of healthcare facility–onset, healthcare facility–associated (HO-HCFA) cases and CO-HCFA cases. We performed interhospital rate comparisons using HO-HCFA cases only and using both HO-HCFA and CO-HCFA cases.

Of 1046 CDAD cases, 442 (42%) were HO-HCFA cases and 604 (58%) were community-onset cases. Of the 604 community-onset cases, 94 (15%) were CO-HCFA, 40 (7%) were of indeterminate exposure, and 208 (34%) community-associated. A modest correlation was found between monthly rates of HO-HCFA cases and CO-HCFA cases across the 6 hospitals (r = 0.63, P<.001). Interhospital rankings changed for 6 of 11 months if CO-HCFA cases were included.

A substantial proportion of community-onset cases of CDAD occur less than 4 weeks after discharge from a healthcare facility, and inclusion of CO-HCFA cases influences interhospital comparisons. Our findings support the use of a proposed definition of healthcare facility–associated CDAD that includes cases that occur within 4 weeks after discharge.