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Healthcare-Associated Infections (HAIs) are a major but preventable patient safety threat. Based on 2002 data, HAIs were estimated to affect approximately 1.7 million persons and contribute to approximately 99,000 deaths annually in the United States.1–3 The annual economic burden of these infections in the United States was estimated at $6.7 billion per year, in 2002 dollars.2

Since no single U.S. surveillance system could provide more refined and updated estimates, a prevalence survey of 10 geographically diverse states that were a part of the Emerging Infections Program, was conducted from 2009 to 2011 in 183 hospitals.4 From this survey, it was projected that 648,000 patients with 721,000 infections were seen among inpatients in 2011. Approximately 4% of the patients had one or more HAIs. The most common types were pneumonia (21.8%), surgical site infections (SSI; 21.8%), and gastrointestinal infections (17.1%). The most common pathogen reported was Clostridioides difficile (C. difficile).4

A repeat survey to assess changes in the prevalence of HAIs showed fewer patients had HAIs in 2015 [394 patients (3.2%; 95% confidence interval {CI}, 2.9–3.5)] than in 2011 [452 (4.0%; 95% CI, 3.7–4.4)] (p < 0.001), largely owing to reductions in the prevalence of surgical-site and urinary tract infections (UTIs). Pneumonia, gastrointestinal infections, most of which were due to C. difficile, and surgical-site infections were the most common HAIs. Patients’ risk of having a HAI was 16% lower in 2015 than in 2011 (risk ratio, 0.84; 95% CI, 0.74–0.95; p = 0.005), after adjustment for age, presence of devices, days from admission to survey, and status of being in a large hospital.4,5

Healthcare in the United States has been increasingly delivered in outpatient, long-term care, and home health settings. Invasive procedures are now frequently performed on an outpatient basis. Although the U.S. population has grown about 38% since the 1970s, the number of hospital admissions remains at 1975 levels (36.3 million in 2002 compared to 36.2 million in 1975); in contrast, the number of outpatient visits has increased 2.5 times (to 640.5 million from 254.8 million).6 Further, the number of certified ambulatory surgical centers increased more than tenfold, from 336 in 1985 to over 5300 in 2013.7 These changes result in an inpatient population that is more likely to have severe illnesses8 and be older.6 Because of this evolution in healthcare, the term “healthcare-associated infection” has become more appropriate and is preferred over “nosocomial infection” or “hospital-acquired infection,” since these latter terms are restricted to the hospital setting.

The epidemiology of HAI in the past was best described in hospital intensive-care units (ICUs); within hospitals, for many years, the highest rates of infections were observed in ICUs.9–11 However, there has been increasing recognition that procedures and exposures, which pose risks of infection, such as the use of central venous catheters (CVC), are also frequent outside ICUs. One ...

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