As I write this, volunteer members of the IUVA are spending long hours in helping with the COVID-19 crisis. Their immediate focus is on how UV can be used by nurses and doctors to deal with the acute shortage of masks, gloves and other personal protective equipment (PPE) in hospitals. A lot of this PPE was designed to be used once and then discarded to avoid the risk of contamination. Now, however, our front-line health professionals are having to risk wearing the same equipment repeatedly in the hopes that some protection is better than none at all. There is clearly the potential for UV to be used to disinfect this equipment between uses, but how should it be done?
Our experience with UV-C devices in the hospital setting is relatively new, and there is not yet good guidance or appropriate protocols. The IUVA recently created a Healthcare Acquired Infections (HAI) focus group to start to address all aspects of UV in the hospital setting, but the COVID-19 crisis has sharpened our focus on PPE. The data on how much UV light is needed to inactivate the SARS-CoV-2 is sparse, but promising. Coronaviruses in general are believed to be very susceptible to UV-C around 254 nm, with controlled studies or predictive modeling showing greater than 4-log inactivation achieved at doses below 20 mJ/cm2. But as those of us who have worked with UV disinfection in the water/wastewater treatment context know, there is a large difference between proving that UV is effective in a lab and proving that it is effective in practice. It doesn’t take much imagination to picture how some viruses might be caught in folds and crevices of PPE during UV treatment.
As an example, there is a study that showed that more than 4000 mJ/cm2 of UV at 254 nm was required to achieve 3-log reduction of MS2 on the surface of masks compared to the 60 mJ/cm2 that is needed under controlled lab conditions (Vo et al., 2009: Applied and Environmental Microbiology). Why the disparity? Were there errors in this study, or is there something fundamentally different about disinfecting on the surface of masks that isn’t captured by the more controlled studies? Right now, we don’t have these answers. Even if the UV treatment is 99.99% effective, the remaining 0.01% might be enough to infect people.
Disinfection is a log reduction game: The process is only as good as how small that last fraction of a percent is. The UV water treatment industry has spent more than 20 years trying to develop protocols to deal with this concept. It’s unreasonable to expect that we’ll have robust answers anytime soon when applying UV in hospitals. But in the meantime, we’re dealing with a pandemic. Common sense dictates that we come up with our best educated guesses quickly, since something is better than nothing. To that end, the IUVA has a dedicated group of experts developing what we hope to be good, rational guidance on using UV in hospitals to deal with the crisis. This IUVA initiative is led by Troy Cowan, Ted Mao and Rick Martinello, with terrific participation from vendors in this sector, medical doctors and others. Thank you, everyone, for your contributions to this emergency response.
This just goes to underscore the need for solid, science-based guidance for the use of UV in the healthcare industry. While the focus right now is on making it safe to reuse PPE, there is still a lot of work to be done on developing best practices for other hospital UV applications – disinfecting bathrooms in intensive care wards, keeping Legionella out of ice dispensing machines and so on. But the promise of UV is enormous. It is an excellent disinfectant and, compared to chemical disinfectants that are in short supply during crises such as this, UV is essentially available as long as there is electricity.
I hope that IUVA members will continue to be engaged in this area once the current crisis passes. We have the opportunity to position ourselves to be far more prepared for challenges to healthcare in the future by using UV in a knowledgeable, responsible and effective way.
