Healthcare-associated infections (HAIs) are infections that patients acquire while receiving medical care in a healthcare facility, and they were not present or incubating at the time of admission. These infections threaten patient safety and public health. Each year, hundreds of millions of patients globally are affected by HAIs, with estimates suggesting about one in 31 hospitalized patients in the United States experiences at least one such infection. The consequences of HAIs include prolonged hospital stays, long-term disability, and increased financial strain on healthcare systems. Understanding this progression is important for prevention.
The Origin of Germs
Infectious agents, often referred to as pathogens, originate from various sources within healthcare settings. Some pathogens come from endogenous sources, meaning they are part of the patient’s own normal body flora, such as bacteria residing on the skin or in the gut. These microorganisms can cause infection if they enter normally sterile areas of the body.
Other pathogens are exogenous, meaning they come from outside the patient’s body. These external sources include other patients, healthcare workers, and visitors who may inadvertently introduce pathogens. The external environment itself, including contaminated surfaces or water sources, can also serve as a reservoir for these infectious agents.
How Germs Spread
Pathogens move through healthcare environments via several common transmission routes. Direct contact transmission occurs when there is physical contact between an infected person or a contaminated surface and a susceptible individual, often involving healthcare workers’ hands. Indirect contact transmission involves the transfer of pathogens through contaminated inanimate objects, known as fomites, such as shared medical equipment not adequately disinfected between uses.
Droplet transmission happens when respiratory droplets, expelled during coughing, sneezing, or talking, travel short distances and deposit on a susceptible person’s mucous membranes. Airborne transmission involves smaller aerosolized particles containing pathogens that can remain suspended in the air for longer periods and travel over greater distances. Common vehicle transmission can occur through contaminated shared items like food, water, or medications.
Patient Vulnerability
Patients in healthcare settings often have factors that increase their susceptibility to infections. A weakened immune system compromises the body’s ability to fight off pathogens. This can result from underlying medical conditions such as cancer, autoimmune diseases, or diabetes.
Certain medical treatments, like chemotherapy or immunosuppressive medications following an organ transplant, also suppress the immune response, leaving patients more vulnerable. Age plays a role, with both very young and elderly patients often having less robust immune defenses. Poor nutritional status can impair immune function, increasing infection risk.
Compromised skin integrity, such as surgical incisions, burns, or pressure ulcers, provides direct entry points for microorganisms, bypassing the body’s natural protective barrier. These breaks in the skin allow pathogens to access deeper tissues, where they can establish an infection.
Role of Medical Procedures and Equipment
Invasive medical procedures and the use of specialized equipment create direct pathways for pathogens to enter the body, bypassing natural defenses like skin and mucous membranes. For instance, the insertion of urinary catheters can introduce bacteria into the urinary tract, leading to catheter-associated urinary tract infections (CAUTIs). Central venous catheters provide a direct route for microorganisms into the bloodstream, causing central line-associated bloodstream infections (CLABSIs).
Surgical incisions, while necessary for treatment, represent open wounds that can become infected if not managed, leading to surgical site infections (SSIs). Mechanical ventilators, used to assist breathing, can introduce pathogens into the respiratory tract, increasing the risk of ventilator-associated pneumonia (VAP). Endoscopes, used for internal examinations, must be properly cleaned and disinfected between uses to prevent the transmission of microorganisms.
The Healthcare Environment’s Contribution
The physical environment within healthcare facilities can serve as a reservoir for pathogens, contributing to their spread. Surfaces that are frequently touched, such as bed rails, call buttons, doorknobs, and sinks, can become contaminated with microorganisms. If these surfaces are not properly cleaned and disinfected, they can facilitate the transfer of pathogens to patients and healthcare workers.
Inadequate ventilation systems can allow airborne particles containing infectious agents to circulate throughout a facility, exposing susceptible individuals. Water systems, including taps, showers, and cooling towers, can harbor bacteria like Legionella, which can be aerosolized and inhaled, leading to severe respiratory infections. The design and maintenance of the healthcare environment play an important role in controlling the spread of infectious agents.