The Need to Understand Infection Risk Sources and Pathways to Mitigate HAIs

By Erin Higgins, MS, CIH, CSP, and Bryan Connors, MS, CIH, HEM

Hospital-acquired infections (HAI) remain a significant source of concern for healthcare facilities of all types and sizes, and the physical environment is often a leading source of these infection-causing pathogens. Data from the CDC indicates that each year, about 1 in 25 U.S. hospital patients are diagnosed with at least one infection related to hospital care alone, and approximately 97,000 Americans die from hospital-related fungal infections each year. While there are many factors that contribute to the prevalence of HAIs, the environment plays a significant role in their transmission.

Industrial hygienists and public health professionals typically rely upon a Source-Pathway-Receptor approach to understanding the infection transmission process. This approach can prove valuable to infection control practitioners as well.

At a high level, the Source-Pathway-Receptor model is as simple as it sounds. To better protect the receptor (most often the patient), often compromised in some way that makes them more suspectable to infections, healthcare facilities need a greater understanding of the typical sources and pathways of infection transmission. By identifying and regularly surveying these common sources and pathways, facilities can implement appropriate controls that will mitigate these risks.

Identifying common sources and pathways

Environmental infection sources fall into a few common categories, including fungi, bacteria, and viruses. These organisms are naturally occurring and can easily amplify in the absence of adequate disinfection, ventilation, and other appropriate mitigation measures. Examples of environmental sources include people, construction or renovation work, and equipment such as cooling towers.

Mitigating the infections these agents cause depends upon exploring possible sources and pathways. For example, a hospital recently called Environmental Health & Engineering, Inc. (EH&E) to search for an environmental cause behind a series of mycobacterial surgical site infections within cardiac patients. An investigation identified that the OR contained a heating-cooling unit with a reservoir that contained potable filtered water and ice from a hospital-grade ice machine. Although the machine was allowed under current best practice, it appeared able to amplify a small amount of mycobacteria normally present within water systems into an amount needed to cause an infection. By using sterile water, which went above and beyond manufacturer recommendations, the source of the mycobacteria from the potable water system was mitigated. In addition, by moving the heater-cooler unit into the sterile OR core outside the positive-pressure patient room, the team was able to disrupt the pathway, thereby further mitigating the infection risk.

A pathway is how an infectious (or opportunistic) agent gets to a host, in this case a patient. Examples of pathways include people, surgical equipment, ventilation systems, and airflow.

In fact, air distribution can be a significant pathway for infection risks. In one recent investigation, EH&E was called to determine why a new OR was seeing an uptick in surgical site infection rates. An engineering study found that the rooms were designed appropriately to reduce infection rates, but the reheat controls were not operating as designed. The result was a brief loss of downflow air in the sterile field over the patient. Although this loss lasted for only a minute or two, it was enough to create a pathway by which infectious agents could reach the vulnerable patient.

Establishing risk surveying protocols

Ideally, a solution to the environmental risks involves addressing both the source and pathway, but this is not always feasible. Consider, for example, that people are the most frequent source of infections. Neither the surgeon nor the patient can be removed from a surgery site. Yet by recognizing people as sources for infection risk and recognizing potential pathways by which infectious agents can travel, infection control professionals can then determine which controls will best mitigate existing risks.

It’s also important to recognize that often these problems lie dormant until there is a change in the environment—one as simple as a loss of pressure or a new staff member unaware of certain protocols. By understanding the potential sources and pathways, healthcare teams can take more protective measures, including appropriate disinfection, equipment maintenance, or monitoring of pressure, relative humidity, and temperature.

Many U.S. healthcare facilities faced a significant environmental change in the early months of the COVID-19 pandemic when ambulatory and surgery centers were closed. The act of not using plumbing and other equipment amplified microbiological agents that are inherent in the water supply. Systems that were not adequately flushed prior to reoccupancy became a pathway for infection risks. Before making any change to the environment, it’s critical to have a plan in place for resuming operations to keep that environment safe.

Building broader environmental awareness

Making the connections from source to pathway to receptor can present a challenge. Often these environmental problems are identified by a core team of infection control professionals and facility management, through multidisciplinary rounds or through risk assessments of the environment of care. However, it is the people working in these environments who often know these rooms best. Physicians, housekeeping personnel, nursing managers, and all other staff members must be made aware of environmental problems’ contribution to HAI rates.

As a case in point, EH&E was called to investigate a skin-related fungal infection in a sensitive inpatient population. An investigation found that the patient room backed up to a resident on-call room whose restroom had a ceiling leak. Over time, a ceiling tile developed mold growth. The source of the infection was the ceiling tile, as it abutted the patient room, and the pathway was the relative air pressure between the on-call restroom and the patient room. It may not have seemed like a problem to the busy residents using that space, but it presented a major risk to the patient in the adjacent room.

The cost of poor prevention

We often hear from health systems that they simply don’t have the resources to expand their facility management oversight. While many health systems are strapped for cash, this is one area where a small investment of time and money can lead to significant savings. Infection prevention is, by far, less expensive than reaction.

In the example described above of the OR that saw an increase in infections due to nonoperational controls, the OR had to be shut down for several months as the investigation was performed. Shutting down an OR for even a few days carries a price tag in the millions, significantly more than the cost of having a staff member check temperature controls on a regular maintenance schedule. Add to that the cost of managing patients for HAIs, many of which are not reimbursable by CMS, and the expenses continue to grow.

By broadening awareness of the environment’s role in infections among not just infection control practitioners but the entire clinical staff, health systems can take a simple yet significant step in further reducing their risk of HAIs.

Erin Higgins is principal consultant of healthcare for EH&E. She leverages deep knowledge of industrial hygiene, infection control, and engineering controls with an up-to-the-minute understanding of United States Pharmacopeia (USP), International Organization for Standardization (ISO), and Occupational Safety and Health Administration (OSHA) compliance to develop sound, cost-effective solutions for healthcare facilities. Bryan Connors directs EH&E’s healthcare practice team, providing guidance and technical support in the areas of environmental health and safety program management, industrial hygiene, hazardous materials management, and regulatory compliance with OSHA, EPA, and Joint Commission requirements.