Disinfection Efficacy of Ultraviolet Light Sources on SARS-CoV-2*

The U.S. Naval Research Laboratory (NRL), in collaboration with the
Naval Surface Warfare Center Dahlgren Division (NSWCDD), has been
tasked with the evaluation of commercial UVC sources and their efficacy
on a SARS-CoV-2 simulant (Phi-6) to support the Navy Coronavirus
Rapid Response Team (NCR2T) at Naval Sea Systems Command
(NAVSEA). As part of the investigation to support both ship and shore
installations for the US Navy, NRL performed optical analysis of a number
of sources such as Hg (254 nm), LED (272 nm and 275 nm), Excimer (222
nm), and Xe (broadband).
NRL measured several optical aspects of the sources, including spectral
output and temporal variation, power density versus space and time, and
operational issues as they may apply to fleet deployment. NSWCDD was
able to use Phi-6, an enveloped RNA virus that has a structure sufficiently
similar to SARS-CoV-2 to function as an adequate BSL-1 surrogate. Phi-6
was prepared to develop BSL-1 enveloped virus test indicators at ≥ 8.0
log 10 coupon −1 . The high virus titer and the capability to ship these BSL-1
coupons enabled quantitation of virus killing at high confidence levels.
Virus-inoculated coupons made of materials such as stainless steel,
keyboard keys, Navy Top Coat, and cardboard were used to evaluate the
efficacy of the UV sources of interest. This paper will discuss the UV
sources evaluated in the NCR2T effort along with the optical and
biological protocols used to estimate the efficacy of the various approaches
available on the commercial market.