Hot, humid air decontamination of aircraft confirmed that high temperature and high humidity are critical for inactivation of infectious, enveloped ribonucleic acid (RNA) virus

Abstract

Aims: To develop infectious (live/dead) enveloped virus test indicators and Response Surface Methodology (RSM) models that evaluate survival of an enveloped ribonucleic acid (RNA) virus on contaminated aircraft materials after exposure to hot, humid air (HHA). Methods and Results: Enveloped RNA bacteriophage Phi6 (φ6) was dried on wiring insulation, aircraft performance coating (APC), polypropylene, and nylon at ≥8 log10 plaque-forming units (PFU) test coupon-1. Only 2.4 log10 inactivation was measured on APC at 70°Celsius (°C), 5% relative humidity (RH) after 24 h. In contrast, HHA RSM models showed a 90% probability of a 7-log10 inactivation at ≥63°C, 90% RH after 1 h, and decontamination kinetics were similar across different materials. HHA decontamination of C-130 and C-17 aircraft showed >7 log10 and ≥5.9 log10 inactivation of enveloped virus on 100 and 110 test indicators, respectively, with a 1-h treatment, excluding ramp-up and ramp-down times. Conclusions: Enveloped RNA virus test indicators were successfully developed, lab tested for HHA decontamination, analyzed for RSM, and field-tested in aircraft demonstrations. Significance and Impact of the Study: The utility of HHA decontamination was demonstrated after inactivating enveloped RNA virus on aircraft with a 1-h HHA treatment within aircraft temperature and RH limits.

Dental Mitigation Strategies to Reduce Aerosolization of SARS-CoV-2

“…Structurally, the Φ6 virus particle is similar to SARS-CoV-2: it is a double-stranded RNA virus of ~80 to 100 nm in size, composed of a lipid membrane envelope and spike proteins (Adams 1959). Recent literature has suggested Φ6 is an appropriate surrogate for infectious enveloped viruses, such as coronavirus (Aquino de Carvalho et al 2017;Prussin et al 2018;Buhr et al 2020;Dubuis et al 2020;Fedorenko et al 2020). Comparing different bacteriophages for viral aerosolization models, Φ6 was shown to behave comparably in nebulization experiments to influenza, another enveloped virus (Turgeon et al 2014).…”

Ultraviolet Dosage and Decontamination Efficacy was Widely Variable across 14 UV Devices after Testing a Dried Enveloped Ribonucleic Acid Virus Surrogate for SARS-CoV-2

“…To increase confidence in decontamination results and to conservatively estimate decontamination requirements for enveloped virus in its native state, enveloped virus test coupons were prepared to be protected similar to a natural virus without interfering with the virus assay. Thus, Φ6 virus was unpurified to maintain natural stabilization with host cell debris and was diluted in a 10% sucrose solution to mimic the presence of carbohydrates in mucus without inhibiting the decontamination assay (Brakke 1951; Malenovska 2014; Buhr et al 2020; Hadi et al 2020; Stadnytskyi et al 2020). In addition, enveloped virus was dried on coupons prior to testing since SARS-CoV-2 respiratory particles evaporate within seconds to generate dry particles, and drying on fomites is also historically documented as a route of infection for enveloped virus (Fenn 2001; Malenovska 2014; Hadi et al 2020; Stadnytskyi et al 2020).…”

“…This only accounts for debris in respiratory particles and does not account for additional debris that might be found on surfaces. In addition, enveloped viruses are more stable in dry conditions compared to wet environments (Cox and Wathes 1995; Chan et al 2011; Buhr et al 2020; Hadi et al 2020; van Doremalen et al, 2013), and drying viruses via lyophilization is frequently used to stabilize virus for long-term storage (Greiff et al 1954; Greiff and Richtel 1966; Malenovska 2014). Hence decontamination kinetics can also be greatly influenced depending on whether the test microbes are wet or dry.…”

“…Viruses that fall under higher World Health Organization (WHO) biosafety level (BSL) classifications such as SARS-CoV-2 (BSL-3) and its BSL-2 surrogate coronaviruses (ASTM International 2020) cannot be widely used in field tests because of cost, time, and safety constraints. For field testing, the enveloped virus surrogate Ф6 was previously used to make “live/dead” Ф6 test indicators to directly test and compare decontamination efficacy across lab and field tests (Buhr et al 2020).…”

Hot, Humid Air Decontamination of Aircraft Confirmed That High Temperature and High Humidity Are Critical for Inactivation of Infectious, Enveloped Ribonucleic Acid (RNA) Virus

“…The aircraft demonstration events involved a consortium of supporters including DTRA, JPEO-CBRND, Aeroclave, LLC, Air Force, Air Mobility Command, United States Transportation Command, Naval Surface Warfare Center-Dahlgren Division, Air Force Research Lab, METSS Corporation, CCDC, and Dover Air Force Base. This manuscript has been released as a pre-print at bioRxiv (Buhr et al, 2020).…”