Table 1.

Risk Factors Associated With Experiencing a COVID-19 Outbreak in Nursing Homes and Long-Term Care Facilities

Risk Factor	References	Summary
Community transmission	22,25,51	•Scotland, N = 334 care homes: Increased likelihood of outbreak with rising community prevalence (OR = 1.2 per 100 cases/100,000 population increase)22 •France, N = 943 nursing homes: Strong correlation (R 2 = 0.71) between population peaks and outbreak peaks in nursing homes25 •Ontario, Canada, N = 770 facilities: Increased likelihood of outbreak with increasing regional prevalence51
Nursing home characteristics
Nursing home size	22,25,51, 52, 53, 54, 55	•Scotland, N = 334 care homes: Increasing facility size (>90 vs <20 beds) linked with increased likelihood of outbreak (adjusted OR: 55)22 •USA, N = 9395 facilities: Increased likelihood in medium (50-150 beds; adjusted OR: 2.63) and large (>150 beds; adjusted OR 6.52) vs small (<50 beds) facilities via public/state reports53 •Systematic review, N = 36 studies in USA: Community prevalence and increasing nursing home size linked to greater likelihood of outbreak52
Nursing home design	56	•USA, N = 219 facilities: Non-traditional “Green House” Design associated with fewer outbreak cases56
Nursing home staffing
Absolute staff numbers	57, 58, 59	•USA: Lowest quartile of unique employees associated with lower deaths than highest quartile (6.2 cases per 100 beds vs 11.9 per 100 beds) in US skilled nursing facilities58 •France, N = 57 nursing homes: Significant correlation between staff and resident cases57 •USA, N = 13,157 facilities: Increasing likelihood of outbreak with greater number of registered nurse hours59
Staff-resident ratio	23,60	•UK, N = 179 facilities: Lower staff-beds ratio an independent risk factor for likelihood of infection23 •England, N = 5126 facilities: Reduced risk (adjusted OR: 0.63) of infection per unit increase in staff-bed ratio60
Staff statutory sick pay available	60	•England, N = 5126 facilities: Statutory sick pay available associated with reduced risk of resident infection (adjusted OR: 0.70)60
Staff cohorting	60	•England, N = 5126 facilities: Not cohorting staff in contact with infected residents associated with greater likelihood of infection (adjusted OR: 1.20)60
Frequent employment of agency nurses and carers	60	•England, N = 5126: Agency staff most days or every day associated with greater likelihood of infection (adjusted OR: 1.85)60
Nursing home quality and for-profit status
Nursing home quality ratings	58,59,61, 62, 63, 64, 65	•USA, N = 123 facilities: Lower likelihood of outbreak with increasing CMS Five-Star Rating62 •USA, N = 713 facilities: Higher CMS rating associated with lower likelihood of outbreak among staff and residents63 •USA, N = 1223 facilities: CMS rating significantly linked to having both resident infection and death64 •USA, N = 15,390: COVID-19 cases and deaths significantly higher in nursing homes with a lower rating65
For-profit status	60,63	•England, N = 5126 facilities: For-profit status associated with increased risk of outbreak (adjusted OR: 1.19)60 •USA, N = 713 nursing homes: Greater outbreak size (12.7 times larger) in for-profit vs nonprofit counterparts63

OR, odds ratio.