Infections acquired in hospitals, known as HAIs or nosocomial infections, are often resistant to antibiotics and thus particularly dangerous. Each year, the estimated 1.7 million infections cause nearly 100,000 deaths in the United States. Many patients in hospitals, nursing homes and clinics become sicker from these infections than they were before they sought care. These infections also play a significant role in costs—HAI hospital costs alone were recently estimated at between $30 and $45 billion.
Current recommendations for reducing hospital-acquired infections target the patient's immediate environment and interactions with care providers. Hand washing by care providers before and after patient contact is a key part of protocols in patient-focused transmission prevention. The wide variety of other measures include identifying patients who enter the hospital with infections for additional isolation, extra care to avoid catheter-associated infections, and augmented surface sanitation—of bed rails and controls, light switches, partition screens, faucet handles, and the like.
Collectively, recommended protocols have been shown to reduce transmission, are cost effective and could be more widely adopted. Still, the attention and effort involved are significant and progress in eliminating infections is slow.
Underlying the widespread prevalence and difficulty in addressing these infections is the large number of contacts between care providers and patients. Because there are so many contacts, the effort involved in making every contact safe is huge and this effort burdens already busy care providers.
How can we speed up progress?
We need to expand our view beyond the point of contact between patients and providers to think in terms of the overall process of transmission within a hospital and between care facilities.
Each transit across a boundary between domains should be considered as a potential “transmission” of pathogens that will infect a unit, ward, floor, building or care facility. At these boundaries, protocols of disinfection should be designed to reduce pathogen transfers from one domain to another. The boundaries between domains should be like airlocks, disinfecting people and objects that pass through them.
What protocols should these boundaries have? Since there are relatively few such crossings as compared to the number of patient contacts overall, we can consider more extensive decontamination procedures than just hand washing, such as clothing sanitation and the cleaning of cell phones and other personal effects. There is evidence that lab coats, PDAs, cell phones and the like act as repositories for pathogens, and can be responsible for HAI transmission. The protocol should still be efficient, and it can be. Staging such intensive interventions at the gateways could significantly reduce the flow of pathogens between patients.
We have to consider how pathogens are transferred: from one patient to the surfaces and fabrics near that patient to the care providers and their clothing, cell phones and pagers. From there the pathogens are transferred either directly to another patient or to the fabrics and surfaces in common areas or around that patient from which they eventually reach that patient at a different contact opportunity.
Most of the possible transmission events happen because of the large number of contacts within a local ward between patients and doctors, nurses, medical technicians, food service people and cleaning staff. Each of these contacts has the potential to transfer pathogens between patients, and to contaminate objects in shared spaces, such as computer keyboards.
If there were no virulent pathogen in the ward in the first place, none of those possible transmission events could actually transfer virulent pathogens. Using boundary protocols to reduce transmission between wards would eliminate a large number of potential transmission events among the individuals within each ward.
With the use of boundary protocols, there would be a reduction not only in the transmission of existing pathogens but also in the emergence of new resistant strains. The high number of physical contacts makes medical care facilities a uniquely fertile environment for pathogens to evolve into more virulent strains. By blocking the spread of infection between areas, we can cut down on the appearance of virulent pathogens as well as their prevalence.
Would everyone have to go through disinfection at these airlocks? Visitors and patients entering a hospital for an appointment don’t present the same level of risk (though they might be tested for infection themselves). Unlike care providers who go from patient to patient to patient, they don’t act as agents for transmission. Accordingly, the same protocols need not apply. Similarly, a caregiver who is only interacting with a single patient need not undergo this process. Furthermore, these protocols could be overridden for the sake of speed in the event of an emergency—when protocols are generally observed, a single contact is unlikely to transmit pathogens.
The same principles of containment are behind biological membranes that prevent transmissions between parts of the body, and are the reason why the immune system is concentrated in the high-speed transport system of the body—the blood. It is the reason we have regulations about plant and animal products crossing national borders. Conversely, the absence of such boundary protections in an increasingly interconnected world has promoted the rise of highly virulent new strains of pathogens and the risks of global pandemics.
Reducing the probability of transmission at each provider-to-patient contact by hand washing and other protocols is still a good idea. At the same time, the flow of pathogens through a hospital and overall transmission between sites can be dramatically reduced. This can be done by creating additional levels of transmission-prevention at key internal boundaries in the care facility and between care facilities.
The cost of hospital-based infections is high and using high-leverage methods to eliminate them is the way to go. By instituting protocols at geographic domain boundaries, at low cost, we can dramatically reduce their transmission.
For Further Reading
1. E. M. Rauch, Y. Bar-Yam, Long-range interactions and evolutionary stability in a predator-prey system, Physical Review E 73, 020903 (2006).
2. L. Leykum, Y. Bar Yam, The rational for system level strategies of infection control. NECSI Report 2010-08 (2010).
3. Department of Health and Human Services, Centers for Disease Control and Prevention, Healthcare-associated infections (HAIs).
4. Agency for Healthcare Research and Quality, Patient Safety Network, Patient safety primer: health care-associated infections.
5. Center for Disease Control, Monitoring hospital-acquired infections to promote patient safety—United States, 1990–1999, Morbidity and Mortality Weekly Report, 49 (3/3/2000).
6. R. M. Klevens, J. R. Edwards, C. L. Richards Jr., T. C. Horan, R. P. Gaynes, D. A. Pollock, D. M. Cardo, Estimating health care-associated infections and deaths in U.S. hospitals, 2002, Public Health Reports 122, 160-166 (2007).
7. R. D. Scott II, The direct medical costs of healthcare-associated infections in U.S. hospitals and the benefits of prevention (2009).
8. R. Wenzel, The economics of nosocomial infections, Journal of Hospital Infection 31, 79-87 (1995).
9. M. R. Eber, R. Laxminarayan, E. N. Perencevich, A. Malani, Clinical and economic outcomes attributable to health care-associated sepsis and pneumonia, Archive of Internal Medicine 170, 347-353 (2010).
10. World Health Organization, Prevention of hospital-acquired infections: a practical guide, 2nd edition (2002).
11. The Department of Health and Human Services, Action plan to prevent healthcare-associated infections (2009).
12. U. S. Government Accountability Office, Health-care-associated infections in hospitals: an overview of state reporting programs and individual hospital initiatives to reduce certain infections (2008).
13. Institute for Healthcare Improvement, Reducing healthcare-associated infections.
14. D. S. Yokoe, L. A. Mermel, D. J. Anderson, et al. A compendium of strategies to prevent healthcare-associated infections in acute care hospitals. Supplement article: executive summary. Infection Control and Hospital Epidemiology 29, S12 (2008).
15. K. K. Macartney, M. H. Gorelick, M. L. Manning, R. L. Hodinka, L. M. Bell, Nosocomial respiratory syncytial virus infections: the cost-effectiveness and cost-benefit of infection control, Pediatrics 106, 520-526 (2000).
16. D. Pittet, S. Hugonnet, S. Harbarth, P. Mourouga, V. Sauvan, S. Touveneau, T.V. Perneger, Effectiveness of a hospital-wide programme to improve compliance with hand hygiene, Lancet 356, 1307–12 (2000).
17. O’Grady, M. Alexander, E. P. Dellinger, J. L. Gerberding, S. O. Heard, D. G. Maki, H. Masur, R. D. McCormick, L. A. Mermel, M. L. Pearson, I. I. Raad, A. Randolph, R. A. Weinstein, Guidelines for the prevention of intravascular catheter–related infections, Infection Control and Hospital Epidemiology 23, 759-769 (2002).
18. J. M. Boyce, D. Pittet, Guideline for hand hygiene in health-care settings: recommendations of the healthcare infection control practices advisory committee and the HICPAC/SHEA/APIC/IDSA Hand Hygiene Task Force, Infection Control and Hospital Epidemiology 23 Supplement, 3-40 (2002).
19. C. A. Muto, J. A. Jernigan, B. E. Ostrowsky, H. M. Richet, W. R. Jarvis, J. M. Boyce, B. M. Farr, SHEA Guideline for Preventing Nosocomial Transmission of Multidrug-Resistant Strains of Staphylococcus aureus and Enterococcus, Infection Control and Hospital Epidemiology 24, 362-386 (2003).
20. T. G. Emori, D. H. Culver, T. C. Horan, W. R. Jarvis, J. W. White, D. R. Olson, S. Banerjee, J. R. Edwards, W. J. Martone, R. P. Gaynes, National nosocomial infections surveillance system (NNIS): description of surveillance methods, American Journal of Infection Control 19,19-35 (1991).
21. S. Fridkin, S. Welbel, R. Weinstein, Magnitude and prevention of nosocomial infections in the intensive care unit, Infectious Disease Clinics of North America 11, 479-496 (1997).
22. C. Steere, G. F. Mallison, Handwashing Practices for the Prevention of Nosocomial Infections, Annals of Internal Medicine 83, 683-690 (1975).
23. W. W. Williams, CDC guideline for infection control in hospital personnel, Infection Control 4, Special Supplement, 326-349 (1983).
24. L. Silvestri, A. J. Petros, R. E. Sarginson, M. A. de la Cal, A. E. Murray, H. K. F. van Saene, Handwashing in the intensive care unit: a big measure with modest effects, Journal of Hospital Infection 59, 172-9 (2005).
25. C. Backman, D. E. Zoutman, P. B. Marck, An integrative review of the current evidence on the relationship between hand hygiene interventions and the incidence of health care-associated infections, American Journal of Infection Control 36 333-348 (2008).
26. T. Eckmanns, F. Schwab, J. Bessert, R. Wettstein, M. Behnke, H. Grundmann, H. Ruden, P. Gastmeir, Hand rub consumption and hand hygiene compliance are not indicators of pathogen transmission in intensive care units, Journal of Hospital Infection 63, 406-411 (2006).
27. N. Duckro, D. W. Blom, E. A. Lyle, R. A. Weinstein, M. K. Hayden, Transfer of vancomycin-resistance enterococci via health care worker hands. Archive of Internal Medicine 165, 302-307 (2005).
28. A. M. Treakle, K. A. Thorn, J. P. Furuno, S. M. Strauss, A. D. Harris, E. N. Perencevich, Bacterial contamination of health care workers' white coats, American Journal of Infection Control 37, 101-105 (2009).
29. J. M. Boyce, Environmental contamination makes an important contribution to hospital infection, Journal of Hospital Infection 65, Supplement 2, 50-54 (2007).
30. A. Kramer, I. Schwebke G. Kampf, How long do nosocomial pathogens persist on inanimate surfaces? A systematic review, BMC Infectious Diseases 6, 130 (2006).
31. S. Bures, J. T. Fishbain, C. F. T. Uyehara, J. M. Parker, B. W. Berg, Computer keyboards and faucet handles as reservoirs of nosocomial pathogens in the intensive care unit, American Journal of Infection Control 28, 465-471 (2000).
32. C. M. Braddy, J. E. Blair, Colonization of personal digital assistants used in a health care setting, American Journal of Infection Control 33, 230-232 (2005).
33. B. C. Eckstein, D. A. Adams, E. C. Eckstein, A. Rao, A. K. Sethi, G. K. Yadavalli, C. J. Donskey, Reduction of Clostridium difficile and vancomycin-resistant Enterococcus contamination of environmental surfaces after an intervention to improve cleaning methods, BMC Infectious Diseases 7, 61 (2007).
34. R. R. W. Brady, S. F. Fraser, M. G. Dunlop, S. Paterson-Brown, A. P. Gibb, Bacterial contamination of mobile communication devices in the operative environment, Journal of Hospital Infection 66, 397-398 (2007).
35. R. R. W. Brady, J. Verran, N. N. Damani, A. P. Gibb, Review of mobile communication devices as potential reservoirs of nosocomial pathogens, Journal of Hospital Infection 71, 295-300 (2009).
36. B. McCaughey, Hospital scrubs are a germy, deadly mess: bacteria on doctor uniforms can kill you, Wall Street Journal (1/8/2009).
37. B. McCaughey, Unnecessary deaths: the human and financial costs of hospital infections: 3rd edition, Committee to Reduce Infection Deaths (RID).
38. L. C. McDonald, W. R. Jarvis, Linking antimicrobial use to nosocomial infections: the role of a combined laboratory-epidemiology approach, Annals of Internal Medicine 129, 245-247 (1998).
39. T. Donker, J. Wallinga, H. Grundmann, Patient referral patterns and the spread of hospital-acquired infections through national health care networks, PLoS Comput Biol 6, e1000715 (2010).
40. M. Lipsitch, C. T. Bergstrom, B. R. Levin, The epidemiology of antibiotic resistance in hospitals: paradoxes and prescriptions, PNAS 97, 1938-1943 (2000).
41. V. Sébille, A. Valleron, A computer simulation model for the spread of nosocomial infections caused by multidrug-resistant pathogens, Computers and Biomedical Research 30, 307-322 (1997).
42. V. Sébille, S. Chevret, A. Valleron, Modeling the spread of resistant nosocomial pathogens in an intensive care unit, Infection Control and Hospital Epidemiology 18, 84-92 (1997).
Writing and Editing Credits
Yaneer Bar-Yam with Luci Leykum, Shlomiya Bar-Yam, Karla Z. Bertrand, and Nancy Cohen
Page 1: "Surgeon washing his hands in an operating room" © iStockphoto / eliandric
Page 2: "Hospital Cutaway" © iStockphoto / Peter Willems
Page 3: Photo by Susan Jensen Smith
Page 4: "Disinfection Gateway Mockup" by Alexander S. Gard-Murray and Yaneer Bar-Yam
Alexander S. Gard-Murray
This work was supported in part by the Centers for Disease Control and Prevention and by an anonymous donation to the New England Complex Systems Institute.