A research study examining the potential role of airborne transmission of SARS-CoV-2, masks as source control, breakthrough infections, and whether breath measurements can be used to improve early diagnosis of infection. (2020-2023)

Public Health Aerobiology Lab at the University of Maryland School of Public Health
Principal Investigator: Dr. Donald K. Milton, MD, DrPH


Infectious Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) in Exhaled Aerosols and Efficacy of Masks During Early Mild Infection, published in Clinical Infectious Diseases (2021). Link to this manuscript:

    • Cases exhale infectious viral aerosols.

    • SARS-CoV-2 is evolving toward more efficient airborne transmission.

    • Loose-fitting masks significantly but moderately reduce viral RNA aerosol.

    • Tight-fitting masks or respirators and ventilation/air cleaning are essential for worker protection in public-facing or crowded indoor workplaces.

    • Please also check out the article at Science News that talks about our results:

Comparison of Saliva and Midturbinate Swabs for Detection of SARS-CoV-2, published in Microbiology Spectrum (2022). Link to this manuscript:

    • We compared detection of SARS-CoV-2 in saliva samples to nasal swab (mid-turbinate) samples.

    • We found that saliva-based PCR is more sensitive than nasal swab-based PCR in detecting SARS-CoV-2 during the presymptomatic period.

    • Since saliva samples cost less, are more acceptable to the general public, and are less of a risk to health care workers, our findings support the use of saliva over naval swabs, in identifying presymptomatic infection by SARS-CoV-2.

Exhaled Breath Aerosol Shedding of Highly Transmissible Versus Prior Severe Acute Respiratory Syndrome Coronavirus 2 Variants, published in Clinical Infectious Diseases (2022). Link to this manuscript:

    • We measured the infectivity and rate of SARS-CoV-2 shedding into exhaled breath aerosols by individuals during the Delta and Omicron waves, and compared those rates with those of prior SARS-CoV-2 variants from our previously published work.

    • We found that Alpha, Delta, and Omicron cases shed significantly more viral RNA in exhaled breath, compared to the earlier SARS-CoV-2 strains.

    • Alpha, Delta, and Omicron independently evolved high viral aerosol shedding phenotypes, demonstrating convergent evolution. Vaccinated and boosted cases can shed infectious SARS-CoV-2 via exhaled breath. These findings support a dominant role of infectious aerosols in transmission of SARS-CoV-2.

Thanks to everyone who took part in this part of the study!!!

In an April 2022 New York Times op-ed, Dr. Donald K. Milton, along with Dr. Edward A. Nardell and Dr. David Michaels, discusses the potential of germicidal ultraviolet light for making indoor environments safer by disinfecting indoor air.

University of Maryland-CERSI/FDA Lecture:

Presented by Donald Milton, MD, DrPH

June 14, 2022

Click HERE to Watch the Recorded Lecture

In a May 2022 CBS interview, Dr. Donald Milton discusses the future of implementing Far UV-C technology as an effective tool to mitigate the spread of air-borne infectious diseases such as COVID-19. This discussion comes at a time when we are still seeing individuals become infected with COVID-19 following the attendance of superspreader events, despite strict testing and vaccination requirements.

For more information about the safety and efficacy of Far-UVC technology, click Here.

Maryland Institute of Environmental Health 688 Seminar:

Results of the UMD StopCOVID Study
High Efficiency Air Sanitation with Germicidal UV Light for Schools and Conference Rooms

presented by Jianyu Lai, MPH and Don Milton, MD, DrPH

Date: Sep 7, 2021

To watch the recording: click HERE

Passcode: !+h8%j?Q

Corsi-Rosenthal Box Builds at the University of Maryland, College Park

Using funding and resources from his recent MPowering the State award, Dr. Donald Milton bought fans, furnace filters and duct tape in bulk for the production of Corsi-Rosenthal boxes at the University of Maryland, College Park. The devices have been shown to effectively improve indoor air quality and ventilation, and are a cost-effective alternative to traditional air purifiers.

Images: Dr. Milton’s PHABlab set up a booth where students, alumni, and community members built their own Corsi-Rosenthal boxes at UMD’s Maryland Day

Congratulations to the StopCOVID Research Team!

Research and Development Award


The study is not accepting any new participants currently.

Study Purpose

This research was being conducted by Donald K. Milton, MD, DrPH and a team of researchers at the University of Maryland with funding from the University and U.S. government agencies.

The purpose was to find out how people transmit COVID-19 and how to prevent transmission.

  • How much airborne virus does an infected person exhale?

  • How much virus is released into the air when an infected person breathes, talks, or sings?

  • How well do surgical and homemade masks block release of airborne virus?

This work will help us understand whether airborne transmission is important and how to prevent it.

Another goal is to gather samples that can be used to better understand how the body fights the infection. This will help with future research to develop new medications and vaccines.