How superbug spreads among regional hospitals: A domino effect

Washington, DC, July 30, 2013 – A moderate increase in vancomycin-resistant enterococci (VRE) at one hospital can lead to a nearly 3 percent increase in VRE in every other hospital in that county, according to a study in the August issue of the American Journal of Infection Control, the official publication of the Association for Professionals in Infection Control and Epidemiology (APIC).

VRE is one of the most common bacteria that cause infections in healthcare facilities.

Researchers from the Johns Hopkins Bloomberg School of Public Health, Pittsburgh Supercomputing Center (PSC), University of Pittsburgh, and University of California, Irvine created the Regional Healthcare Ecosystem Analyst (RHEA), a mathematical and computational model, to track the movement between hospitals of VRE-colonized patients (patients carrying the organism but not yet infected) over the course of a year in Orange County, Calif. Using this model, they were able to assess how increases or decreases in one hospital's VRE affected neighboring hospitals.

Not only did the investigators find that a moderate increase in VRE at any one hospital caused an average 2.8 percent increase throughout the county (range: 0 percent to 61 percent), they also discovered that hospitals in the most populated area of the county had an even greater likelihood of spreading VRE throughout the network. Additional modeling identified a potential for "free-riders"—hospitals that will experience decreases in VRE incidence due to other hospitals' infection control efforts without initiating any infection prevention measures of their own.

The study points to the underutilization of patient-sharing data between regional hospitals, the importance of inter-hospital communication and collaboration in decreasing VRE rates, and the scope of variables that must be considered in analyzing the outcome of any one infection prevention initiative.

"Our study demonstrates how extensive patient sharing among different hospitals in a single region substantially influences VRE burden in those hospitals," state Bruce Y. Lee, MD MBA, lead author and Associate Professor of International Health and Director of Operations Research, International Vaccine Access Center, at the Johns Hopkins Bloomberg School of Public Health. "Lowering barriers to cooperation and collaboration among hospitals, for example, developing regional control programs, coordinating VRE control campaigns, and performing regional research studies, could favorably influence regional VRE prevalence."

Vancomycin-resistant enterococci are resistant to vancomycin, the drug often used to treat serious infections for which other medicines may not work. VRE can live in the human intestines and female genital tract without causing disease. However, sometimes they can cause infections of the urinary tract, the bloodstream, or of wounds associated with catheters or surgical procedures. There are an estimated 20-85,000 cases of VRE each year in U.S. hospitals.


AJIC: American Journal of Infection Control ( covers key topics and issues in infection control and epidemiology. Infection preventionists, including physicians, nurses, and epidemiologists, rely on AJIC for peer-reviewed articles covering clinical topics as well as original research. As the official publication of APIC, AJIC is the foremost resource on infection control, epidemiology, infectious diseases, quality management, occupational health, and disease prevention. AJIC also publishes infection control guidelines from APIC and the CDC. Published by Elsevier, AJIC is included in MEDLINE and CINAHL.


APIC's mission is to create a safer world through prevention of infection. The association's more than 14,000 members direct infection prevention programs that save lives and improve the bottom line for hospitals and other healthcare facilities. APIC advances its mission through patient safety, implementation science, competencies and certification, advocacy, and data standardization. Visit APIC online at Follow APIC on Twitter: and Facebook:


"Modeling the regional spread and control of vancomycin-resistant enterococci," by Bruce Y. Lee, S. Levent Yilmaz, Kim F. Wong, Sarah M. Bartsch, Stephen Eubank, Yeohan Song, Taliser R. Avery, Richard Christie, Shawn T. Brown, Joshua M. Epstein, Jon I. Parker and Susan S. Huang appears in the American Journal of Infection Control, Volume 41, Issue 8 (August 2013).


Bruce Y. Lee, MD, MBA (Corresponding Author)
Public Health Computational and Operations Research (PHICOR), Johns Hopkins Bloomberg School of Public Health, Baltimore, MD.

S. Levent Yilmaz, PhD
Center for Simulation and Modeling, University of Pittsburgh, Pittsburgh, Pa.

Kim F. Wong, PhD
Center for Simulation and Modeling, University of Pittsburgh, Pittsburgh, Pa.

Sarah M. Bartsch, MPH
PHICORJohns Hopkins Bloomberg School of Public Health, Baltimore, MD.

Stephen Eubank, PhD
Network Dynamics and Simulation Science Laboratory, Virginia Bioinformatics Institute, Blacksburg, Va.

Yeohan Song, BS
PHICOR, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD

Taliser R. Avery, MS
Department of Population Medicine, Harvard Medical School and Harvard Pilgrim Health Care Institute, Boston, Mass.

Richard Christie, PhD
Center for Simulation and Modeling, University of Pittsburgh, Pittsburgh, Pa.

Shawn T. Brown, PhD
Pittsburgh Supercomputing Center, Carnegie Mellon University, Pittsburgh, Pa.

Joshua M. Epstein, PhD
Department of Emergency Medicine, Johns Hopkins University, Baltimore, Md.

Jon I. Parker, MS
Department of Emergency Medicine, Johns Hopkins University, Baltimore, Md.

Susan S. Huang, MD, MPH
Division of Infectious Diseases and Health Policy Research Institute, University of California, Irvine, Calif.