Something in the Air: New Data Suggests SARS-CoV-2 Airborne Transmission
The emergence of a novel coronavirus (SARS-CoV-2) at the end of December 2019 rapidly spread across the globe, causing a pandemic and catching the world unprepared. The incredibly fast dissemination throughout countries and populations left scientists scrambling to uncover how exactly the virus is transmitted. The SARS-CoV-2 virus, causing the disease COVID-19, can be fatal in many cases. The United States has been affected harder than any country in the world, with over 6.8 million cases and over 200,000 deaths (1) at the time of this writing.
Understanding the mechanisms of transmission is necessary to develop public health guidance for prevention such as cleaning and disinfection practices, ventilation, proper personal protective equipment (PPE) use, and hand hygiene. Recent evidence is continuing to emerge on how SARS-CoV-2 is transmitted, with alarming support that airborne transmission may be a bigger contributing factor to its spread than initially thought. This blog discusses mode of transmission, including dialogue around emerging technology and practices to combat the spread of the virus.
The transmission of SARS-CoV-2 is known to spread more efficiently than influenza, but not as efficiently as measles.(2) It initially was thought to spread mainly person-to-person through larger respiratory droplets produced when an infected person coughs, sneezes or talks. These droplets have weight to them and are only able to successfully travel about six feet from a person before they fall to the ground. Additionally, the virus has been thought to spread in other ways, such as through touching contaminated surfaces and then touching the mouth, nose or eyes, and rarely, through exposure to infected animal hosts.
Now though, as the pandemic continues to spread throughout the world, it has been noted that the virus may be an opportunistic airborne traveler under the right conditions. Airborne transmission differs from droplet transmission in that the infected particles can travel a much further distance (10. For example, imagine a person sitting at the center of a movie theater. In droplet transmission only the people in a six-foot radius of the infected person will subsequently be exposed to the disease, whereas if the infectious particles are airborne, the entire theater could possibly be exposed and infected. In another analogy, that same person is eating an orange. The persons within a six feet radius are likely to not only smell the orange but also get sprayed by droplets as the orange is peeled- this is droplet transmission. Although, the rest of the theater attendees may not be sprayed by droplets, eventually as the air currents make their way around the room, they likely will be able to smell the peeled orange – this is airborne transmission.
Is SARS-CoV-2 airborne?
The developing school of thought around the possibility of airborne transmission largely started because of the “super-spreader” event (12). For example, during a choir practice on March 10th in Skagit County Washington out of the 61 people attending, 53 were infected (87% attack rate), 3 were hospitalized and 2 died, all from exposure to one infected individual in the same room for 2.5 hours.(3) Many other documented similar “super-spreader” events have led scientists to continue to discuss and research the possible airborne route of transmission. Although at first reluctant to state that SARS-CoV-2 is airborne, the World Health Organization (WHO) acknowledged its possibility in a briefing on July 9, 2020. The WHO stated, “Outside of medical facilities, some outbreak reports related to indoor crowded spaces have suggested the possibility of aerosol transmission, combined with droplet transmission, for example, during choir practice, in restaurants, or in fitness classes. In these events, short-range aerosol transmission, particularly in specific indoor locations, such as crowded and inadequately ventilated spaces over a prolonged period-of-time with infected persons cannot be ruled out (4).”
With this alarming proof in mind, what can health care facilities do to help mitigate the spread and transmission of such a pathogen? Are there proven technologies to help?
In the study titled “How can airborne transmission of COVID-19 indoors be minimized?”, published in September of 2020 in the Environment International, the authors support the use of UV light as an adjunct strategy in a layered approach which also includes proper ventilation and air circulation/filtration, wearing of PPE, and avoiding overcrowding (5). They state:
“Several studies show that inactivation decreases with increased humidity for both bacterial and viral aerosols. Darnell et al. (2004) showed that SARS-CoV-1 could be inactivated by UV-C, while Bedell et al. (2016) showed a UV-C decontamination device could inactivate MERS-CoV at 1.22 m, with almost a 6-log reduction in 5 min. There is no data yet for SARS-CoV-2, but the data for other coronaviruses suggest it is highly likely that it is susceptible to UV-C.”
UV light has, in fact, long been used in healthcare settings to combat transmissible pathogens including tuberculosis which is a well-known airborne pathogen (11. The UV wavelength is capable of inactivating microorganisms and is germicidal. It is also chemical and residual-free, which is good as it leaves no harsh smells for the next patient like some liquid disinfectants.
Multiple studies on the use of UV light technology as an approach to disinfection have shown a decrease in common healthcare-associated infections (HAIs), including Clostridioides difficile. (6) In a multi-center cluster-randomized crossover study performed in 9 U.S. based hospitals called the “BETR-D” study, the researchers concluded that the use of UV light technology as a strategy for disinfection reduced the incidence of the target organisms by 30%. (7) Although no position has been taken yet by the FDA or the EPA, the International Ultraviolet Association believes that UV light can help prevent transmission of SARS-CoV-2. They state:
“The International Ultraviolet Association (IUVA) believes that UV disinfection technologies can play a role in a multiple barrier approach to reducing the transmission of the virus causing COVID-19, SARS-CoV-2, based on current disinfection data and empirical evidence. UV is a known disinfectant for air, water and surfaces that can help to mitigate the risk of acquiring an infection in contact with the COVID-19 virus when applied correctly (9)”.
UV light is a very promising way to potentially prevent airborne and contact transmission of SARS-CoV-2, however, more studies are needed.
The disinfection of surfaces also needs to continue to be a priority, with transmission of virus from the environment onto people’s hands. Studies have shown that viruses can easily travel in such a way. For example, when a study was done using labeled phages the researchers stated that “viruses can spread from a single contaminated door handle or the hands of 1 infected person to people and equipment throughout an office building within hours”. (8) The use of an EPA approved intermediate level disinfectants for the cleaning and disinfection of surfaces should be used for COVID-19 prevention in the environment of care. The EPA has a list of disinfectants approved for use against SARS-CoV-2 which can be found on LIST N. PDI has a wide range of surface disinfectants effective against coronaviruses and approved on list N.
A Layered Approach to Infection Prevention:
As the world continues to battle this virus and the evidence continues to mount that transmission may be driven also by airborne and not just droplet methods, the need for effective ways to prevent person to person spread will be at the forefront of the research priorities.
A layered approach to infection prevention which includes appropriate handwashing, improved ventilation systems, wearing of personal protective equipment (such as masks), a robust environment of care cleaning and disinfection program with EPA list-N approved products — along with adjunct technology such as UV light decontamination, will continue to be key ways people and healthcare facilities can help mitigate the risk of spread of microorganisms.
For more about PDI’s Layered Approach to Infection Prevention, download our latest Infographic.
- Hamner L, et al. MMWR 2020; 69 (19): 606-610.
- “How can airborne transmission of COVID-19 indoors be minimised?” Linda Morawska et al. Environment International Volume 142, September 2020, 105832.
- Anderson, D., Gergen M., Smathers E., Sexton DJ., Chen LF., Weber DJ., et al. Decontamination of targeted pathogens from patient rooms using an automated ultraviolet C-Emitting device. Infection Control Hospital Epidemiology 2013; 34: 466-71.
- Deverick J Anderson, Luke F Chen, David J Weber, Rebekah W Moehring, Sarah S Lewis, Patricia F Triplett, Michael Blocker, Paul Becherer, J Conrad Schwab, Lauren P Knelson, Yuliya Lokhnygina, William A Rutala, Hajime Kanamori, Maria F Gergen, Daniel J Sexton. Enhanced terminal room disinfection and acquisition and infection caused by multidrug-resistant organisms and Clostridium difficile (the Benefits of Enhanced Terminal Room Disinfection study): a cluster-randomised, multicentre, crossover study. January 16, 2017. The Lancet, Vol 389, No. 10071, 905-814.
- Reynolds KA, Beamer PI, Plotkin KR, Sifuentes LY, Koenig DW, Gerba CP. The healthy workplace project: reduced viral exposure in an office setting. Arch Environ Occup Health. 2016;71(3):157-162.
- International Ultraviolet Association IUVA Fact Sheet on COVID-19.
- 2007 Guideline for Isolation Precautions: Preventing Transmission of Infectious Agents in Healthcare Settings page 19. https://www.cdc.gov/infectioncontrol/pdf/guidelines/isolation-guidelines-H.pdf
- 11 The History of Ultraviolet Germicidal Irradiation for Air Disinfection. Nicholas G. Reed. UV Germicidal Irradiation for Air Disinfection, public health reports, Jan-Feb. 2010, vol 125. S. Army Center for Health Promotion and Preventive Medicine, Laser/Optical Radiation Program, Aberdeen Proving Ground, MD.
- Wrong person, place and time: viral load and contact network structure predict SARS-CoV-2 transmission and super-spreading events. Ashish Goyal, Daniel B Reeves, E. Fabian Cardozo-Ojeda, View ORCID ProfileJoshua T Schiffer, Bryan T. Mayer. doi: https://doi.org/10.1101/2020.08.07.20169920