Center for Disease Dynamics, Economics & Policy

According to the US Centers for Disease Control and Prevention, 1 in 20 Americans admitted to hospitals is infected while receiving treatment for another condition. More than 48,000 people die each year of infections that are acquired in healthcare settings. And each year, 18,650 deaths follow infection with methicillin-resistant Staphylococcus aureus (MRSA), a pathogen that is now easily transmitted in both community and healthcare settings. MRSA bacteremia significantly increases the length of hospital stays, the charges per patient, and hospital costs per case. According to a large-cohort study at Duke University Medical Center (Durham, NC), MRSA in surgical wounds resulted in more than a 12-fold increase in mortality vs. that in uninfected patients and more than a 3-fold increase vs. that in patients infected with methicillin-sensitive S. aureus (MSSA). The average total cost of treatment for a patient with an MRSA infection was ∼$40,000 more than for a patient with an MSSA infection and ∼$84,000 more than for an uninfected patient.

The continued high rates of MRSA in US hospitals indicate that healthcare facilities remain unswayed by the high costs of MRSA. One reason may be that the additional costs of hospital infections are borne by Medicare and other third-party payers rather than the hospital itself, and therefore hospitals have little incentive to act. The report by Ke et al. in PNAS provides evidence in support of another reason. If there are large spillovers of antibiotic-resistant bacteria among medical care facilities because of patient movement, there may be little incentive for any single facility to invest in infection control. In other words, because a hospital (especially in the current era of cost cutting and financial pressures) may not realize the benefits of its hospital infection control program because of the incoming flow of infections (Fig. 1), it may prefer to free-ride on the infection control investments of other hospitals. The incentive to free-ride increases with the number of hospitals that share patients with the focal institution and results in an overall higher level of MRSA.