Hospitalizations among family members increase the risk of MRSA infection in a household.

Objective: Estimate the risk for household transmission of Methicillin-Resistant Staphylococcus aureus (MRSA) following exposure to infected family members or family members recently discharged from a hospital.

Design: Analysis of monthly MRSA incidence from longitudinal insurance claims using the Merative MarketScan Commercial and Medicare (2001-2021) databases.

Setting: Visits to inpatient, emergency department, and outpatient settings.

Patients: Households with ≥2 family members enrolled in the same insurance plan for the entire month.

Methods: We estimated a monthly incidence model, where enrollees were binned into monthly enrollment strata defined by demographic, patient, and exposure characteristics. Monthly incidence within each stratum was computed, and a regression analysis was used to estimate the incidence rate ratio (IRR) associated with household exposures of interest while accounting for potential confounding factors.

Results: A total of 157,944,708 enrollees were included and 424,512 cases of MRSA were identified. Across all included enrollees, exposure to a family member with MRSA in the prior 30 days was associated with significantly increased risk of infection (IRR: 71.03 [95% CI, 67.73-74.50]). After removing enrollees who were hospitalized or exposed to a family member with MRSA, exposure to a family member who was recently discharged from the hospital was associated with increased risk of infection (IRR: 1.44 [95% CI, 1.39-1.49]) and the risk of infection increased with the duration of the family member's hospital stay (P value < .001).

Conclusions: Exposure to a recently hospitalized and discharged family member increased the risk of MRSA infection in a household even when the hospitalized family member was not diagnosed with MRSA.