Urinary tract infections are the most common nosocomial (hospital-acquired) infection, accounting for more than 30% of all infections reported by acute care hospitals. The vast majority of these are linked to urinary catheters. Roughly 5% of all hospitalized patients in the United States develop at least one healthcare-associated infection during their stay, and globally that figure rises to about 8.7%.
Why Urinary Tract Infections Lead the List
Most hospital-acquired UTIs are catheter-associated. Every day a urinary catheter stays in place, the risk of bacteria entering the bladder rises by 3% to 10%. Because millions of patients receive catheters during surgery, critical care, or routine hospital stays, the sheer volume of exposure makes UTIs far more common than any other type of hospital infection. The bacteria most frequently responsible is E. coli, which ranks as the single most common pathogen across all healthcare-associated infections, causing 16.2% of reported cases.
Other Major Types of Hospital Infections
While UTIs are the most frequent, several other categories make up a significant share of infections acquired in healthcare settings.
Surgical site infections occur in 2% to 4% of patients undergoing inpatient surgery, making them the most common preventable complication after an operation. Each case adds an average of roughly $28,000 in hospital costs.
Bloodstream infections tied to central lines (the IV catheters placed in large veins for medication or nutrition) are less common but far more dangerous. A single case adds an average of about $48,000 in costs and carries a high risk of sepsis.
Ventilator-associated pneumonia develops in patients on mechanical breathing support, typically in intensive care. It carries a per-case cost burden similar to bloodstream infections, averaging around $47,000.
C. difficile infections deserve special mention because they sit at the intersection of hospital exposure and antibiotic use. Antibiotics disrupt the normal gut bacteria, allowing C. difficile to take over and cause severe diarrhea and colon inflammation. In 2023, the CDC recorded about 117 cases per 100,000 people at its surveillance sites. Each case adds roughly $17,000 in hospital costs.
The Pathogens Behind These Infections
CDC surveillance data from 2018 to 2021 reveals which organisms cause the most trouble in hospitals. E. coli tops the list at 16.2% of all reported pathogens, followed by Staphylococcus aureus at 11.3%. When grouped by genus, Enterococcus species collectively account for 14.4%, and Candida (a fungus rather than a bacterium) makes up 7.5%.
What makes these pathogens especially concerning is antibiotic resistance. More than half of S. aureus infections in intensive care units are MRSA, meaning they resist the standard antibiotics used for staph infections. Nearly a quarter of Enterococcus isolates in ICUs are resistant to vancomycin, one of the last-resort drugs. Among gram-negative bacteria like Pseudomonas and Klebsiella, resistance to broad-spectrum antibiotics has climbed steadily, making some infections extremely difficult to treat.
Who Is Most at Risk
Any hospitalized patient can develop a nosocomial infection, but several factors sharply increase the odds. The most important is having an invasive device: a urinary catheter, a central line, or a ventilator. The longer the device stays in, the higher the risk. ICU patients face the greatest exposure because they often have all three simultaneously.
Age, weakened immune function, prolonged hospital stays, and recent antibiotic use all compound the risk. Antibiotics, while necessary, wipe out protective bacteria and create openings for resistant organisms and C. difficile.
How Hospitals Reduce These Infections
The most effective prevention strategies are surprisingly straightforward. Hand hygiene is the single most impactful measure, and hospitals track compliance rates as a core performance metric. Beyond handwashing, the CDC outlines several standard practices: proper cleaning and disinfection of surfaces, safe injection and medication handling, appropriate use of gloves and gowns, and careful reprocessing of reusable medical equipment between patients.
For catheter-associated UTIs specifically, the biggest gains come from simply removing catheters as soon as they are no longer needed. Many hospitals now use daily checklists prompting clinicians to reassess whether each catheter is still necessary. Similar “bundle” approaches exist for central lines and ventilators, combining several evidence-based steps into a standard protocol.
The Financial Weight of Hospital Infections
Across the five major infectious categories tracked by federal agencies (catheter-associated UTIs, central line bloodstream infections, surgical site infections, ventilator-associated pneumonia, and C. difficile), the average additional cost per case is approximately $31,000. That figure represents the extra expense above what the same hospitalization would have cost without the infection, covering longer stays, additional treatments, and complications. Catheter-associated UTIs, despite being the most common, carry a relatively lower per-case cost of about $13,800. Bloodstream infections and ventilator-associated pneumonia are the most expensive individual events, each approaching $48,000 per case.