Transmission dynamics of epidemic methicillin-resistant Staphylococcus aureus and vancomycin resistant enterococci in England and Wales

A simple epidemiological framework for the analysis of the transmission dyn amics of hospital outbreaks of epidemic methicillin-resistant Staphylococcu s aureus (EMRSA) and vancomycin-resistant enterococci (VRE) in hospitals in England and Wales is presented. Epidemic strains EMRSA-15 and EMRSA-16 are becoming endemic in hospitals in the United Kingdom, and theory predicts t hat EMRSA-15 and EMRSA-16 will reach respective endemic levels of 158 (95% confidence interval [CI], 143-173) and 116 (95% CI, 109-123) affected hospi tals with stochastic fluctuations of up to 30 hospitals in each case. An ep idemic of VRE is still at an early stage, and the incidence of hospitals ne wly affected by VRE is growing exponentially at a rate r = 0.51/year (95% C I, 0.48-0.54). The likely impact of introducing surveillance policies if ac tion is taken sufficiently early is estimated. Finally, the role of heterog eneity in hospital size is considered: "Super-spreader hospitals" may incre ase transmission by 40%-132% above the expected mean.