Influenza Virus Aerosols in Human Exhaled Breath: Particle Size, Culturability, and Effect of Surgical Masks

MedicalResearch.com Author Interview: Dr. Donald K. Milton, MD, Dr.P.H

dr_donalk_k_miltonDr. Donald K. Milton, MD, Dr.P.H
Professor and Director
Maryland Institute for Applied Environmental Health
University of Maryland

MedicalResearch.com: What are the main findings of the study?

Dr. Milton: We found that total viral copies detected by molecular methods were 8.8 times more numerous in fine (≤5 µm) than in coarse (>5 µm) aerosol particles and that the fine particles from cases with the highest total number of viral RNA copies contained infectious virus.

Surgical masks reduced the overall number of RNA copies by 3.4 fold.

MedicalResearch.com: Were any of the findings unexpected?

Dr. Milton: Yes, the higher numbers in the fine aerosol particles was surprising, because larger droplets have much greater volume and might be expected to contain larger numbers of viral copies.

MedicalResearch.com: What should clinicians and patients take away from your report?

Dr. Milton: Surgical masks, while not as effective as PPE against fine particle aerosols, can limit the amount of virus shed into small particles by patients. Thus, they may be useful as infectious aerosol control, even if aerosols turn out to be important for influenza virus transmission.

MedicalResearch.com:  What recommendations do you have for future research as a result of this study?

Dr. Milton: Future research to understand the primary mode of influenza transmission should consider that only a small number of the 37 patients we studied generated almost all of the virus aerosol we detected. This may mean that airborne transmission is mainly driven by the presence of a small number of superspreaders.

Citation: Milton DK, Fabian MP, Cowling BJ, Grantham ML, McDevitt JJ (2013) Influenza Virus Aerosols in Human Exhaled Breath: Particle Size, Culturability, and Effect of Surgical Masks. PLoS Pathog 9(3): e1003205. doi:10.1371/journal.ppat.1003205