The COVID-19 pandemic has amplified the necessity for a significant methodological shift in infection prevention measures, pivoting away from droplet-based precautions towards a framework that addresses transmission of infectious agents ‘through the air’, across varying particle sizes. Owing to the simultaneous circulation of pathogens such as measles, SARS-CoV-2, and influenza, a heightened focus on creating core prevention strategies like enhanced ventilation, the use of respirators, and the endorsement of higher air change rates in healthcare facilities has become paramount.
The SARS-CoV-2 pandemic has sparked renewed urgency to prevent infections from pathogens that spread through the air. The longstanding, pathogen-specific droplet guidance precautions are gradually giving way to a paradigm which emphasizes a continuum of particle sizes and the factors resulting in their airborne projection. Small particles (<100 μm) can become aerosolized and remain suspended in the air longer, potentially holding higher concentrations of an infectious agent.
Such airborne pathogens can emerge from various everyday actions like breathing, talking, spitting, sneezing, or even flushing toilets. Healthcare facilities currently face the challenge of managing three key airborne infectious agents in the United States: seasonal flu, SARS-CoV-2 and measles. Each possesses different propensities for infection and can spread both through the air and on surfaces. Dealing with these pathogens necessitates deploying strategies that target the contagious agent with the highest potential to spread.
It’s noteworthy that maximizing indoor air changes per hour (ACH) can considerably curb the spread of airborne pathogens like seasonal flu, as suggested by recent studies. An air change refers to replacing room air with clean air, an action pivotal in removing airborne contaminants. However, the air circulation within an enclosed space can be uneven leading to some areas of the room being cleaned or replaced more frequently than others.
The American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) have published guidelines, ASHRAE Standard 241, on controlling infectious aerosols. Apart from using high-efficiency particulate air (HEPA) air purifiers, circulating outdoor air and utilizing germicidal UV-C lights can contribute to achieving desired ACH levels. However, conditions like a location’s industrial pollution levels will influence the type of Heating, Ventilation, and Air Conditioning (HVAC) system used in a facility.
The advent of SARS-CoV-2 and the sustained transmission of airborne pathogens cautions us towards a narrative that considers these airborne pathogens as the ‘cost of doing business’. This consideration has significant implications and may demand drastic upgrading of HVAC systems, enabling them to meet the challenges of the current infectious diseases landscape which goes far beyond the guidelines provided by CDC in 2003.