GAINESVILLE, Fla. — New research from the University of Florida provides strong evidence that aerosol transmission of SARS-CoV-2, the virus that causes COVID-19, may be possible.
Prior to these findings, which are in pre-print and have not undergone peer review, the virus had been detected in aerosols, but there was a lack of direct evidence that the particles were actually viable (“culturable”)1, so to date the World Health Organization and other public health agencies have not emphasized aerosol transmission in their public health protection and mitigation guidance.
A team of UF researchers, led by John Lednicky, Ph.D., and Chang-Yu Wu, Ph.D., found that SARS-CoV-2 in aerosols can be cultured, sparking the need to reevaluate current safety protocols to reduce transmission in indoor spaces.
The researchers collected air samples that contained culturable SARS-CoV-2 from the air of a hospital room with COVID-19 patients. The team used a unique virus aerosol sampler, co-developed with Aerosol Dynamics Inc., that gently collects airborne viruses and preserves their viability.
The sampler uses water vapor condensation-based technology to efficiently collect virus aerosols, accomplishing a task not possible using other devices. They were able to obtain viable viruses more than 15 feet away from the patient, contained within the room, and they matched the virus in the air to that in a nasal swab from that patient. Once the samples were collected, Lednicky, an expert virologist and aerobiologist, was able to isolate the virus in cell cultures, resolving the long-standing question of whether SARS-CoV-2 can remain viable in aerosols.
“The air we breathe is full of microorganisms. A pathogen that you breathe poses no harm if it is not alive. For example, non-viable, or ‘dead,’ viruses cannot cause COVID-19, just like a dead tiger can’t eat you. By showing that viable viruses are in the air, we show there is an inhalation risk. We are the first group to show this conclusively,” Lednicky said.
Importantly, virus was not located in hospital hallways or other areas, including the emergency room waiting room, showing the effectiveness of infection control practices.
The findings have stimulated fervent discussion. Virginia Tech’s Linsey Marr, Ph.D., a leading expert on airborne virus transmission, calls it the “smoking gun.”
“Our research opens a new door for analyzing outbreaks due to respiratory viruses. It is especially valuable for those involving asymptomatic individuals or those who have mild symptoms, who are often missed by current epidemiology and surveillance practices during assessments of outbreaks caused by respiratory viruses. That is because those people are typically not tested, yet may be seeding the air with infectious virus particles that pose a risk to others. Instead of relying on human specimens, aerosol sampling is a noninvasive and effective technique for collecting airborne respiratory viruses, and thus has many important and practical uses,” Wu said.
The key researchers of the multidisciplinary team include: Chang-Yu Wu, Ph.D., a professor in the Engineering School of Sustainable Infrastructure & Environment in the Herbert Wertheim College of Engineering at UF; John Lednicky, Ph.D., a professor in the department of environmental and global health at the UF College of Public Health and Health Professions and a member of the UF Emerging Pathogens Institute; Michael Lauzardo, M.D., deputy director of the Emerging Pathogens Institute and J. Glenn Morris, M.D., director of the Emerging Pathogens Institute, both of whom are faculty members in the UF College of Medicine; and Thomas B. Waltzek, Ph.D., an associate professor in the department of infectious diseases & immunology at the UF College of Veterinary Medicine and a member of the Emerging Pathogens Institute.
1Viable: In virology, the term ‘viable’ is used instead of ‘live’. To determine if virus is viable, it must be isolated (“cultured”) in a susceptible animal or in laboratory cell cultures. Thus, if a virus is “culturable”, it is viable virus because it can invade a cell and complete its life cycle within the cell (it can invade the cells and replicate therein to form progeny virus particles that can go on to infect additional cells).
For further information on the study, visit https://www.medrxiv.org/content/10.1101/2020.08.03.20167395v1.
UF Engineering School of Sustainable Infrastructure & Environment
Reba Liddy Hernandez
UF College of Public Health and Health Professions
UF Emerging Pathogens Institute
Nicolle Michaels Roberts