Healthcare-Associated Infections (Hospital-Acquired Infections)

What counts as a healthcare-associated infection

An HAI is not an infection you brought into hospital. Doctors generally count it as healthcare-associated when it:

• starts 48 hours or more after admission
• appears within 30 days of surgery, or up to 90 days after an implant such as a joint replacement or pacemaker
• develops after a stay in a nursing home, long-term care facility or dialysis unit
• is linked to a device such as a catheter, IV line or ventilator

"Hospital-acquired" and "nosocomial" infections are the hospital subset of HAIs.

Main types of healthcare-associated infection

Surgical site infections and pneumonia are the most common in US hospitals, followed closely by gastrointestinal infections, mostly C. diff colitis.

Antibiotic-resistant germs

Many HAIs are caused by bacteria that resist common antibiotics, including MRSA, vancomycin-resistant enterococci (VRE), and carbapenem-resistant Enterobacterales (CRE). The yeast Candida auris has also spread in some hospitals and nursing homes. Resistant infections are harder to treat and spread between patients on hands, equipment and surfaces.

Why infections happen in healthcare settings

• Devices bypass the body's defenses: catheters, IV lines and breathing tubes give germs a direct route into the bladder, blood or lungs. Risk rises with every day a device stays in.
• Surgery breaks the skin barrier.
• Patients are already vulnerable: illness, older age, diabetes, cancer treatment and malnutrition weaken immunity.
• Antibiotics disrupt normal gut bacteria, allowing C. diff to take over.
• Germs spread on hands of staff and visitors, shared equipment and surfaces.

Symptoms to watch for

HAIs can start in hospital or after you go home. Watch for:

• fever, chills or feeling suddenly unwell
• new confusion or drowsiness, especially in older adults, where it may be the only sign
• redness, swelling, warmth, pus or a bad smell from a wound or line site
• frequent watery diarrhea
• new cough, breathlessness or chest pain
• pain on urinating, or pain in the lower belly or side

Diagnosis and treatment

Doctors examine wounds and device sites and order blood cultures, urine or sputum cultures, wound swabs, stool tests for C. diff, and a chest X-ray when pneumonia is suspected. Treatment depends on the type:

• Removing or replacing the infected device is often essential.
• Antibiotics chosen to cover likely resistant germs, then narrowed when culture results return.
• Surgery or drainage for deep wound infections or abscesses.
• Specific C. diff treatment (oral vancomycin or fidaxomicin) and stopping unnecessary antibiotics.
• Isolation precautions (gowns, gloves, single rooms) to stop spread.

The most dangerous complication is sepsis, the body's extreme response to infection, which needs emergency treatment.

How hospitals prevent HAIs

• Hand hygiene before and after every patient contact
• Checklists for inserting and maintaining central lines and catheters, with daily reviews of whether they are still needed
• Skin cleaning and correctly timed antibiotics before surgery
• Raising the head of the bed and daily breathing-tube assessments for ventilated patients
• Antibiotic stewardship programs to avoid unnecessary or overly broad antibiotics
• Cleaning rooms with products that kill C. diff spores
• Screening and isolation for resistant organisms

What you can do as a patient or visitor

• Ask staff, politely, whether they have cleaned their hands. Clean your own hands often, especially before eating.
• Ask every day: "Do I still need this catheter or IV line?"
• Before surgery, stop smoking, keep blood sugar controlled and follow skin-washing instructions. Do not shave the surgical area yourself.
• Tell staff if a dressing becomes loose, wet or dirty, or a line site is sore.
• Take antibiotics only when prescribed and ask why they are needed.
• Get flu, COVID-19 and pneumococcal vaccines as recommended.
• Visitors who are sick, especially with vomiting or diarrhea, should stay home.

Frequently asked questions

What are the most common hospital-acquired infections?

In US acute care hospitals, the most common are pneumonia, surgical site infections and gastrointestinal infections, mainly C. diff. Bloodstream infections from central lines and urinary infections from catheters are also tracked closely because they are largely preventable.

What is the difference between a nosocomial infection and a healthcare-associated infection?

Nosocomial means hospital-acquired. Healthcare-associated is broader and includes infections picked up in nursing homes, dialysis centers, outpatient surgery and other care settings. In everyday use the terms overlap.

How long after surgery can an infection appear?

Most surgical site infections appear within 30 days. Infections around implants such as artificial joints, mesh or heart devices can appear up to 90 days later, and occasionally later still. Report fever, wound redness, drainage or increasing pain promptly.

Are healthcare-associated infections preventable?

Many are. Studies estimate that a large share of central line and catheter infections can be prevented with checklists, prompt device removal and hand hygiene. Not every HAI is avoidable, because some patients are very ill and need devices for a long time.

Can I catch an infection from visiting someone in hospital?

The risk to healthy visitors is low. Clean your hands on entering and leaving, follow any isolation signs such as wearing gowns and gloves, and stay away if you are unwell. People with weak immunity should ask staff before visiting patients in isolation.