Recent research into COVID-19 suggests that health care systems need to move beyond the idea that pathogen spread happens either via droplets or aerosolized particles. Patients can generate the full range of respiratory particles.
The innumerable problems with health care systems in the United States and the rest of the world that were exposed by COVID-19 continue to keep medical investigators busy. They are finding yet more dimensions to the pandemic that has stomped about since March 2020.
At the beginning of the pandemic, experts struggled to understand just how the SARS-CoV-2 virus spreads: by droplets or particles? But that might not be the right question.
In a review published in November 2021 in the Annals of Internal Medicine (AIM),1 Michael Klompas, MD, MPH, an infectious disease expert and a professor of population medicine at Harvard Medical School in Boston, Massachusetts, and his colleagues argue that division of droplet and aerosol transmission is misguided and needs to be retired.
Michael Klompas, MD, MPH
There are viruses such as influenza and mumps that spread by relatively large droplets produced by coughing and sneezing and that fall to the ground relatively quickly. Doctors, nurses, and other clinicians are advised to wear face masks to block the droplets.
Other pathogens are aerosolized, spreading via minute respiratory particles that individuals produce when they talk and breathe. Aerosols tend to stay suspended in the air for much longer periods of times than droplets and travel much farther.
As an article in ICT® pointed out in October 2020, perhaps the best analogy for COVID-19 would be how cigarette smoke can linger and spread in an enclosed setting such as a bar (back when smoking was allowed in those establishments).2 In such a situation, 6-foot social distancing offers very little protection.
Measles and tuberculosis are 2 examples of viruses that spread this way. Precautions against aerosols include N95 masks, negative-pressure rooms, ventilation, and high-efficiency particulate air (HEPA) filters.
Klompas et al argue that research into COVID-19 and the SARS-CoV-2 virus demonstrates that individuals generate the full range of respiratory particles, not just either droplets or aerosols. Aerosolized droplets can stay aloft for long periods, and respiratory viruses are not picky about the size of particle that they hitch a ride on. However, aerosols may account for most transmission, partly because individuals produce aerosols just by talking and breathing.
The governing factor of transmission, wrote Klompas et al, is infectious dose—the amount of virus an individual is exposed to. Infectious dose is a product of time and exposure concentration, or how much virus is in the air, the authors wrote. Poor ventilation can allow virus-laden aerosols to accumulate and increase the exposure concentration and, as a result, the infectious dose. Good ventilation, HEPA filters, and ultraviolet disinfection can decrease the amount of virus floating in the air.
Source strength—or how much virus an infected individual is spewing into the air in respiratory particles—is another factor in the complicated question, the authors explained.
Klompas et al discussed some of the implications of the current understanding of respiratory virus transmission for infection control policies and programs. Here is their list of potential policy responses, which was included in the AIM review:
This article originally appeared in Managed Healthcare Executive®.
References:
Stay prepared and protected with Infection Control Today's newsletter, delivering essential updates, best practices, and expert insights for infection preventionists.
Reducing Hidden Risks: Why Sharps Injuries Still Go Unreported
July 18th 2025Despite being a well-known occupational hazard, sharps injuries continue to occur in health care facilities and are often underreported, underestimated, and inadequately addressed. A recent interview with sharps safety advocate Amanda Heitman, BSN, RN, CNOR, a perioperative educational consultant, reveals why change is overdue and what new tools and guidance can help.
New Study Explores Oral Vancomycin to Prevent C difficile Recurrence, But Questions Remain
July 17th 2025A new clinical trial explores the use of low-dose oral vancomycin to prevent Clostridioides difficile recurrence in high-risk patients taking antibiotics. While the data suggest a possible benefit, the findings stop short of statistical significance and raise red flags about vancomycin-resistant Enterococcus (VRE), underscoring the delicate balance between prevention and antimicrobial stewardship.
What Lies Beneath: Why Borescopes Are Essential for Verifying Surgical Instrument Cleanliness
July 16th 2025Despite their smooth, polished exteriors, surgical instruments often harbor dangerous contaminants deep inside their lumens. At the HSPA25 and APIC25 conferences, Cori L. Ofstead, MSPH, and her colleagues revealed why borescopes are an indispensable tool for sterile processing teams, offering the only reliable way to verify internal cleanliness and improve sterile processing effectiveness to prevent patient harm.
The Next Frontier in Infection Control: AI-Driven Operating Rooms
Published: July 15th 2025 | Updated: July 15th 2025Discover how AI-powered sensors, smart surveillance, and advanced analytics are revolutionizing infection prevention in the OR. Herman DeBoard, PhD, discusses how these technologies safeguard sterile fields, reduce SSIs, and help hospitals balance operational efficiency with patient safety.
Targeting Uncertainty: Why Pregnancy May Be the Best Time to Build Vaccine Confidence
July 15th 2025New national survey data reveal high uncertainty among pregnant individuals—especially first-time parents—about vaccinating their future children, underscoring the value of proactive engagement to strengthen infection prevention.