Viruses in the Built Environment. Linsey C. Marr Civil and Environmental Engineering

Transcription

1 Viruses in the Built Environment Linsey C. Marr Civil and Environmental Engineering

2 Acknowledgments Students and Post-Docs Ellen Garcia Peeyush Khare Kaisen Lin AJ Prussin II Mari Lee Eric Vejerano Wan Yang Faculty Subbiah Elankumaran Seema Lakdawala Peter Vikesland

3 Engineering Approach O - + O O transport R R salt R R transport ph transformation source of emissions exposure or deposition

4 Sources of Airborne Microbes HVAC system mold outdoors humans plants plumbing pets dust resuspension (Prussin and Marr, 2016, Microbiome)

5 Total Virus Concentration Concentration (# L -1 ) 1,400 1,200 1, Viruses Bacteria (Prussin and Marr, 2015, ES&T Letters)

6 Seasonality Month J F F M M A A M M J J J J J A A S S O O N N D D D J J Adenovirus not detected RSV Rotavirus not detected HVAC filters in daycare center 16S rrna sequencing for bacteria PCR for 6 targeted viruses Blank filter was positive for enterovirus-71, influenza A, rhinovirus (Prussin and Marr, 2015, PLoS One)

7 Aerosol Size Defines Transport 0.1 m 0.5 m

8 Influenza A in Airplanes, Daycare, Health Center 70% smaller than 2.5 m (Yang et al., 2011, J. Roy. Soc. Interface)

9 K = turbulent diffusivity, varies with height Resuspension 2 2 turbulent transport source gravitational settling (Khare and Marr, 2015, Indoor Air)

10 Virus Dynamics Indoors ventilation inactivation dc dt d v ( H k) C d settling concentration of infectious viruses in aerosols of diameter d Settling velocity v = f(d), and d = f(rh) Inactivation rate k = f(rh) (Yang and Marr, 2011, PLoS One)

11 Virus-Aerosols From a Cough C/ d eq (# m -3 µm -1 ) λ = 1 ACH at RH = 50% evaporation and gravitational settling 0 min 1 min 5 min 10 min 15 min 30 min 45 min d eq (µm) There is a size shift due to loss of larger droplets by gravitational settling. (Yang and Marr, 2011, PLoS One)

12 Infectious Concentrations v. RH 20 C/ d eq (# m -3 µm -1 ) % RH 30% RH 50% RH 70% RH 90% RH d eq (µm) Concentrations are higher at lower RH because inactivation rate is lower. (Yang and Marr, 2011, PLoS One)

13 Humidity and Viability? final/initial diameter m 1 m % 20% 40% 60% 80% 100% RH (Yang and Marr, 2011, PLoS One)

14 Humidity Evaporation Chemistry Low RH (<50%) Efflorescence occurs solutes cannot harm virus Medium RH salt mucin Very high RH Minimal evaporation physiological conditions are maintained solutes in droplet crystallize 20 m Elevated solute concentrations or ph may harm virus (Yang and Marr, 2012, Appl. Environ. Microbiol.)

15 Summary There are widespread sources of viruses in the built environment. Airborne viruses are subject to aerosol dynamics. Virus stability depends on humidity. Future challenges include viral metagenomics, interactions with bacteria and fungi, virus microenvironment. (Prussin et al., 2014, FEMS Microbiol. Letters) Sources Transport Transformations Next

16 References 1. Khare, P., Marr, L.C., (2015). Simulation of vertical concentration gradient of influenza viruses in dust resuspended by walking, Indoor Air, 25(4), Prussin II, A.J., Marr, L.C., (2015). Sources of airborne microorganisms in the built environment, Microbiome, 3, Art. no Prussin II, A.J., Garcia, E.B., Marr, L.C., (2015). Total concentrations of virus and bacteria in indoor and outdoor air, Environmental Science & Technology Letters, 2(4), Prussin II, A.J., Vikram, A., Bibby, K.J., Marr, L.C., (2016). Seasonal dynamics of the airborne bacterial community and selected viruses in a children's daycare center, PLoS ONE, 11, e Prussin II, A.J., Marr, L.C., Bibby, K.J., (2014). Challenges of studying viral aerosol metagenomics and communities in comparison with bacterial and fungal aerosols, FEMS Microbiology Letters, 357(1), Titcombe Lee, M., Pruden, A., Marr, L.C., (2016). Partitioning of viruses in wastewater systems and potential for aerosolization, Environmental Science & Technology Letters, 3, Yang, W., Elankumaran, S., Marr, L.C., (2012). Relationship between humidity and influenza A viability in droplets and implications for influenza's seasonality, PLoS ONE, 7(10), e Yang, W., Marr, L.C., (2012). Mechanisms by which ambient humidity may affect viruses in aerosols, Applied and Environmental Microbiology, 78, Yang, W., Marr, L.C., (2011). Dynamics of airborne influenza A viruses indoors and dependence on humidity, PLoS ONE, 6(6), e Yang, W., Elankumaran, S., Marr, L.C., (2011). Concentrations and size distributions of airborne influenza A viruses measured indoors at a health centre, a day-care centre and on aeroplanes, Journal of the Royal Society Interface, 8(61),