Loss of Infectivity of Influenza Virus During Aerosol Sampling
JIN PAN, Nisha Duggal, Seema Lakdawala, Meher Sethi, Nahara Vargas Maldonado, Vedhika Raghunathan, Anice Lowen, Linsey Marr, Virginia Tech
Abstract Number: 174
Working Group: Bioaerosols
Abstract
Our understanding of transmission of influenza virus and other respiratory viruses is limited by the ability to detect infectious virus in aerosol particles. In environmental samples, viral RNA is often recovered, but infectious virus has rarely been detected. Most aerosol sampling methods are believed to contribute to virus inactivation, but the magnitude of this sampling artifact is unknown. To investigate this question, we aerosolized influenza A virus suspended in human saliva into a small chamber. Aerosols were allowed to settle for 10 min onto either Madin-Darby canine kidney (MDCK) cells or a thin layer of Minimum Essential Medium (MEM) in Petri dishes. The sample in MEM was immediately transferred to MDCK cells. Aerosols that deposited directly onto cells led to the formation of ~100 plaques per dish. In contrast, aerosols that deposited first onto MEM led to the formation of only 0-2 plaques. Further experiments ruled out uneven aerosol distribution in the chamber or inefficient virus recovery as causes for this discrepancy. These findings indicate that aerosolized influenza A virus lost infectivity by approximately 2 log10 plaque forming units (PFU) within ~10 min unless it attached to cells quickly. As natural infection via inhalation occurs by direct deposition of virus onto cells, we hypothesize that sampling directly onto cells more accurately reflects the potential for exposure to lead to infection, whereas traditional aerosol sampling methods result in underestimation of the risk. In future work, we will evaluate the loss of infectivity of virus after deposition onto other collection substrates, such as agar and gelatin. We will also compare influenza virus to other respiratory viruses, such as SARS-CoV-2, to test our hypothesis.