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Public Health Aerobiology Laboratory (PHAB Lab)

Studying Airborne Infection Transmission

Dr. Donald Milton testing out his machine with a student

The laboratory supports studies of:

  • airborne infection transmission
  • influenza epidemiology
  • bioaerosol exposure in asthma
  • non-invasive monitoring of exhaled biomarkers

Capabilities of the lab include culturing viruses, RTqPCR, analysis of exhaled breath particles, bioaerosol sampling and immunoassay.

Department: Applied Environmental Health (MIAEH)
Room Number: 0110, 0117, 0120, 2131A
Director: Donald Milton

Office Phone Number: (301) 405-3142
Find Don Milton on Mastodon for the medical community 
Find Don Milton on Mastodon for the science community 

The Public Health Aerobiology Lab is led by Dr. Donald Milton. The lab studies infectious diseases in exhaled breath.

Our sponsors include:

UMD StopCOVID illustration



Recent Publications From the Public Health Aerobiology Laboratory

Lai J, Coleman KK, Tai S-H, German J, Hong F, Albert B, Esparza Y, Srikakulapu A, Schanz M, Sierra Maldonado I, Oertel M, Fadul N, Gold TL, Weston S, Mullins K, McPhaul KM, Frieman M, Milton DK. Exhaled Breath Aerosol Shedding of Highly Transmissible Versus Prior Severe Acute Respiratory Syndrome Coronavirus 2 Variants, Clinical Infectious Diseases (2022), ciac846.

Lai J, German J, Hong F, Tai S-H, McPhaul K, Milton DK, University of Maryland StopCOVID Research Group. Comparison of Saliva and Midturbinate Swabs for Detection of SARS-CoV-2, Microbiology Spectrum (2022).

Adenaiye O, Lai J, Bueno de Mesquita PJ, Hong F, Youssefi S, German J, Tai S-H, Albert B, Schanz M, Weston S, Hang J, Fung C, Chung HK, Coleman KK, Sapoval N, Treangen T, Maljkovic Berry I, Mullins K, Frieman M, Ma T, Milton DK, University of Maryland StopCOVID Research Group. Infectious Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) in Exhaled Aerosols and Efficacy of Masks During Early Mild Infection, Clinical Infectious Diseases (2021), ciab797.

Prather K, Marr L, Schooley R, McDiarmid M, Wilson M, Milton DK. Airborne Transmission of SARS-CoV-2, Science 05 Oct 2020

Milton DK. A Rosetta Stone for Understanding Infectious Drops and Aerosols. J Pediatric Infect Dis Soc 2020
(accepted manuscript here if you cannot access journal webpage)

Morawska L, Milton DK. It is Time to Address Airborne Transmission of COVID-19. Clin Infect Dis 2020

Bueno de Mesquita PJ, Noakes CJ, Milton DK. Quantitative aerobiologic analysis of an influenza human challenge-transmission trial. Indoor Air 2020

Bueno de Mesquita PJ, Nguyen-Van-Tam J, Killingley B, et al. Influenza A (H3) illness and viral aerosol shedding from symptomatic naturally infected and experimentally infected cases. Influenza Other Respir Viruses 2020; irv.12790.

Chia PY, Coleman KK, Tan YK, et al. Detection of air and surface contamination by SARS-CoV-2 in hospital rooms of infected patients. Nature Communications 2020;11(1):2800.

Morawska L, Tang JW, Bahnfleth W, et al. How can airborne transmission of COVID-19 indoors be minimised? Environ Int 2020;142:105832.

Nguyen-Van-Tam JS, Killingley B, Enstone J, et al. Minimal transmission in an influenza A (H3N2) human challenge-transmission model within a controlled exposure environment. PLoS Pathog 2020;16(7):e1008704.

Leung NHL, Chu DKW, Shiu EYC, et al. Respiratory virus shedding in exhaled breath and efficacy of face masks. Nature Medicine 2020;1–5.

Zhu S, Jenkins S, Addo K, et al. Ventilation and laboratory confirmed acute respiratory infection (ARI) rates in college residence halls in College Park, Maryland. Environment International 2020;137:105537.

Fennelly KP, Acuna-Villaorduna C, Jones-Lopez E, Lindsley WG, Milton D. Microbial Aerosols: New Diagnostic Specimens for Pulmonary Infections. CHEST [Internet] 2019 [cited 2019 Nov 20];0(0).

Yan J, Grantham M, Pantelic J, et al. Infectious virus in exhaled breath of symptomatic seasonal influenza cases from a college community. Proc Natl Acad Sci USA 2018;115(5):1081–6.

Recent News Coverage of UMD StopCOVID Team Members

September 7, 2021 Maryland Institute of Environmental Health 688 Seminar:

Results of the UMD StopCOVID Study and High Efficiency Air Sanitation with Germicidal UV Light for Schools and Conference Rooms, presented by Jianyu Lai, MPH and Don Milton, MD, DrPH

View the zoom recording for MIEH 688 Seminar September 7, 2021.

Passcode: !+h8%j?Q

Infectious SARS-CoV-2 in Exhaled Aerosols and Efficacy of Masks During Early Mild Infection: We have analyzed the results of 13 months of the StopCOVID study. The manuscript is available at [], and is undergoing review for publication.

Key points:

  • 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 these results:

Here's Why Mouthwash Is Not Going To Save You From Coronavirus. (November 17, 2020).
UMD Scientists Say Vice Presidential Debate Needs Air Filtration System Due To Coronavirus. CBS Baltimore, October 7, 2020.
Beyond Plexiglass: Scientists Say This Simple Solution Could Keep VP Debate Safer. NPR, October 7, 2020.
The plexiglass barriers at tonight’s debate will be pretty useless, virus experts say. New York Times, October 7, 2020.
Answering COVID's Big Questions on Campus. Maryland Today, October 6, 2020.
The Flu May Linger in the Air, Just Like the Coronavirus. The New York Times, July 14, 2020.
We Need to Talk About Ventilation. Tufekci Z. The Atlantic. July 30, 2020.

Recent Lectures by Members of the UMD StopCOVID Team

Virtual Press Conference on COVID-19 Science Letter October 5, 2020
Dr. Milton's lecture for MIEH 688: Infectious Drops and Aerosols September 22, 2020
University of California San Francisco Medical Grand Rounds July 16, 2020: Dr. Milton
A Conversation: What Do Science and Data Say About the Near Term Future of Singing May 5, 2020 Webinar

    Principal Investigator: Dr. Donald Milton

    Research and Clinical Faculty: Dr. Barbara Albert, Dr. Kristen Coleman, Dr. Jennifer German, Dr. Kate McPhaul, Dr. Sheldon Tai

    Faculty Specialists: Dr. Filbert Hong, Isabel Sierra Maldonado, Louie Gold

    Staff: Yi Esparza, Maria Schanz, Faith Touré, Rhonda Washington-Lewis

    Graduate Research Associates: Jianyu Lai

    Alumni: Dr. P. Jacob Bueno de Mesquita, Aaron Kassman, Michael Lutchenkov, Delwin Suraj, Dr. Somayeh Youssefi

    See the website of our current project: UMD StopCOVID

    Evaluating Modes of Influenza Transmission (EMIT-2)

    Sponsor: National Institute of Allergy and Infectious Diseases

    Participating Institutions/Departments: UMD SPH, UMD Clark School of Engineering, UMD CBMG; UMSOM in Baltimore; University of Hong Kong School of Public Health; Icahn School of Medicine at Mt. Sinai; Global Health Institute at the University of Wisconsin-Madison; University of Michigan School of Public Health; Aerosol Dynamics

    EMIT-2 organization of projects and cores
    Project 1 (Evaluating Modes of Influenza Transmission using a Randomized Controlled Trial, EMIT-2-RCT)
    Lead Investigator: Don Milton, UMD SPH
    Co-Investigators: Ben Cowling, HKU SPH; Aubree Gordon, UMich SPH; Florian Krammer, Mt. Sinai School of Medicine
    1. Identify the dominant mode of transmission using naturally infected influenza donors in an RCT of air sanitation-ventilation and hand hygiene-face shield interventions.
    2. Determine the impact of aerosol exposure on disease severity.
    3. Investigate the impact of serologic and mucosal antibody levels on influenza transmission, susceptibility and immunologic response to infection.
    Project 2 (Developing and Applying Analytical Models of Influenza Transmission)
    Lead Investigator: Jelena Srebric, UMD ENG
    Co-Investigators: Aubree Gordon, UMich SPH; Gabriele Neumann, UWis GHI
    1. Support the cohort study experimental setup: face shield, ventilation, UR-GUV application
    2. Develop two analytical models for source characterization:
      - A high-fidelity model to identify variability in risk due to temporal and spatial distributions of virus concentration.
      - A well-mixed model (for well-mixed conditions) using CO2 as a stand-in to assess viral aerosol exposure and dose.
    3. Apply the analytical models to house cohort & ferret studies
    Clinical and Biostatistics Core (CBC)
    Lead Investigator: Wilbur Chen, UMSOM
    Co-Investigators: Justin Ortiz, Shuo Chen, UMSOM
    1. Provide regulatory and safety infrastructure for a randomized controlled trial of influenza transmission.
    2. Screen for health adult volunteers (Recipients), willing to temporarily reside on an inpatient containment unit for approximately 2 weeks during the influenza season, and index cases with acute influenza infection (Donors).
    3. Expose un-infected eligible volunteers (Recipients) to influenza-infected index case patients (Donors).
    Advanced Bioaerosol Technology Core (ABTC)
    Lead Investigator: Don DeVoe, UMD ENG
    Co-Investigators: Meg Scull, Gregg Duncan, UMD CMBG; Arantza Eiguren-Fernandez, Greg Lewis, Aerosol Dynamics; Yoshihiro Kawaoka, Gabriele Neumann, UWis GHI
    1. Develop a compact platform for ambient sampling and culture.
    2. Develop an instrument for efficient exhaled breath sampling.
    3. Develop a hydrogel collection target and an optimized cell line for enhanced infectivity analysis.
    4. Develop a digital culture microarray to study distribution of viable virus in aerosols.

    Center for Research on Influenza Pathogenesis and Transmission (CRIPT) @ UMD

    Human-to-Human Transmission Studies (aka the WhereFlu? Study)

    Part of the NIAID Centers of Excellence for Influenza Research and Response (CEIRR)
    Sponsor: National Institute of Allergy and Infectious Diseases (NIAID)

    Principal Investigator: Don Milton (UMD SPH)
    Co-Investigators: Kathleen Stewart (UMD BSOS), Jelena Srebric (UMD ENG), Charles Ma (UMD SPH)

    Aim 1: Identify influenza outbreaks and hotspots for transmission and characterize ventilation of campus buildings to test the hypothesis that building ventilation at <5 L/s/person is associated with localized influenza outbreaks.
    • This cohort is meant to represent the population served by the University Health Center (UHC).
    • The influenza cases that present at the UHC are the core of the cohort.
      • The infection data will integrate with environmental data from:
      • Academic buildings
      • Campus shuttle buses
      • 37 residence halls
    • Multiple neighboring apartment complexes
    • Longitudinal surveillance of influenza infections seen at the UHC, combined with geospatial and temporal analysis of residence, work/class location, and shuttle bus ridership, will identify outbreaks and hotspots.

    Aim 2: Using data from UMD Dormitory Cohort studies and a counterfactual model matching influenza cases-contacts pairs from high and low ventilation residence halls, test the hypothesis that building ventilation <5 L/s/person is associated with increased risk of transmission.
    • Our Dormitory Cohrots are dynamic cohorts recruited annually from 1,500 undergraduate students in living-learning communities in five residence halls.
    • Collected from cases and contacts:
      • Questionnaires 
      • Biological specimens (sera, swabs, and PBMCs) 
      • Exhaled breath aerosol samples
      • Paired smartphone swabs
    • Counterfactual analysis of case-contact pairs in neighboring high- and low-ventilation buildings.
    • Our initial analyses with CRIPT will focus on existing samples and data from 2017-20 Prometheus@UMD cohorts.

    StopCOVID study

    Inquire at


    Find out how people transmit COVID-19 and how to prevent transmission:

    1. How much airborne virus does an infected person exhale?
    2. How much virus is released into the air when an infected person breathes, talks, or sings?
    3. How well do surgical and homemade masks block release of airborne virus?

    Another goal is to gather samples that can be used to better understand how the body fights the infection.

    UMD StopCOVID illustration
    Illustration of how viruses spread via air from an infected person, both with and without a mask.
    • Kingfisher Duo nucleic acid preparation workstation
    • QuantStudio7 with TaqMan Array Card qPCR system
    • Two Qiagen QiaCube robotic nucleic acid preparation workstations
    • Agilent Mx3005P qPCR system
    • Biotek ELX808IU and FLX800TBIE visible and fluorescence temperature controlled kinetic microplate readers,
    • three CO2 incubators,
    • a biosafety cabinet,
    • two Gesundheit-II human exhaled aerosol collectors (an additional device at National University of Singapore)
    • a human exhaled aerosol droplet sampler with cryogenic impactor ("IcePac")
    • four Pulmatrix Exhalair exhaled particle analyzer and collectors
    • assorted aerosol generators for liquid droplet and dry aerosols
    • HEPA filtered glove box and large chamber for aerosol containment
    • Vaisala CO2 monitors
    • air sampling pumps
    • and upper-room UVC fixtures.

    Prometheus@UMD (2017-2020)


    Prometheus@UMD diagram









    Website (historical):

    1. Identify and characterize contagious phenotype of acute respiratory infection (ARI)
    2. Identify biomarkers of infection and contagiousness
    3. Test wearable sensors for early detection of ARI & outbreaks
    4. Collect PBMCs for identification of epigenetic markers of infection
    5. Characterize the role of aerosols and built environment in ARI transmission
    Description of Effort:
    • Enroll a longitudinal cohort and obtain baseline serology
    • Identify index cases of ARI using 45plex TAC assay & enroll contacts
    • Follow contacts with daily respiratory swabs and blood samples
    • Characterize viral shedding in resp. & fomite swabs, and exhaled breath
    • Confirm transmission events through phylogenetics sequencing
    • Monitor indoor environment CO2, temperature, rel. humidity, and estimate re-breathed air exposures
    • Analyze peripheral blood via RNA sequencing from days before onset of infection for biomarkers of infection and contagiousness
    • Cohort in the Wild
    • Fully computerized consent, questionnaire, & lab data collection
    • Daily surveys for respiratory symptoms (via text SMS)
    • Built Environment – natural experiment – high/low ventilation dorms
    • Virology and Infectious Disease (PHAB Lab & Frieman Lab at UMSOM)
    • Bioinformatics, Biostatistics (phylogenetics, machine learning)
    • Antigen arrays/Immunome (Felgner Lab at UC-Irvine)
    • Aerobiology and exhaled biomarkers (aerosol shedding)
    • Mechanical Engineering (indoor air, ventilation)
    • Computer Science (location tracking)
    • Student research assistants – lab and clinical experience


    Year 1 (spring 2017): $1.6M
    • Longitudinal cohort: 74 students
    • 72 ARI cases; 60 contacts followed; PAXgene: 123 total, 7 Day 0/-1
    • 9 Flu A, 1 FluB, 15 AdV, 3 RSVA, 9 RSVB, 25 hCoV, 4 hPIV
    Year 2 (2017-2018): $2.5M
    • Longitudinal cohort: 284 students
    • 76 ARI cases; 70 contacts followed; PAXgene 193 total, 8 Day 0/-1
    • 6 Flu A, 9 Flu B, 5 AdV, 4 RSVB, 24 hCoV, 13 hPIV, 1 hMPV
    Year 3 (2018-2019): $2.9M
    • Longitudinal cohort: 575 participants
    • 211 ARI cases screened; 137 contacts followed
    • PAXgene: 927 total, 44 Day 0/-1; PBMC 339 total, 43 acute ARI
    • Daily text message, average response rate: 248
    • Wearable devices deployed: 150; 29 validated ARI among users
    • 27 Flu A, 4 AdV, 3 RSVA, 6 RSVB, 56 hCoV, 11 hPIV, 11 hMPV
    Year 4 (2019-20): $2.1M
    • Wearable devices cohort: 250
    • 78 ARI cases screened; 46 contacts followed
    • PAXgene: 384 sample-days, 32 Day 0/-1
    • 3 Flu A, 6 Flu B, 1 RSVA, 1 RSVB, 18 hCoV, 2 hPIV, 7 hMPV