SARS-CoV-2 Inactivation in Aerosol by Means of Radiated Microwaves

Abstract

Coronaviruses are a family of viruses that cause disease in mammals and birds. In humans, coronaviruses cause infections on the respiratory tract that can be fatal. These viruses can cause both mild illnesses such as the common cold and lethal illnesses such as SARS, MERS, and COVID-19. Air transmission represents the principal mode by which people become infected by SARS-CoV-2. To reduce the risks of air transmission of this powerful pathogen, we devised a method of inactivation based on the propagation of electromagnetic waves in the area to be sanitized. We optimized the conditions in a controlled laboratory environment mimicking a natural airborne virus transmission and consistently achieved a 90% (tenfold) reduction of infectivity after a short treatment using a Radio Frequency (RF) wave emission with a power level that is safe for people according to most regulatory agencies, including those in Europe, USA, and Japan. To the best of our knowledge, this is the first time that SARS-CoV-2 has been shown to be inactivated through RF wave emission under conditions compatible with the presence of human beings and animals. Additional in-depth studies are warranted to extend the results to other viruses and to explore the potential implementation of this technology in different environmental conditions.

Comment on Manna et al. SARS-CoV-2 Inactivation in Aerosol by Means of Radiated Microwaves. Viruses 2023, 15, 1443

“…In a recent article published in Viruses by Manna et al [ 1 ], the authors estimate the resonant frequency of SARS-CoV-2 particles using elastic continuum theory of the vibrational modes of a sphere [ 2 ]. Unfortunately, the article provides an incorrect solution to the eigenvalue equation.…”

“…The peak absorption frequency from spectroscopy can then be used as the centre of a frequency range to test for inactivation experiments [ 7 , 9 , 10 ]. Alternatively, Lamb’s equation can be used to calculate the dipolar resonant frequency across the size range of the virus, which indicates a frequency range over which inactivation can be tested [ 1 , 15 ]. However, while the dimensions of many viruses have been measured using electron microscopy, acoustic properties are only available for a single virus (STMV [ 16 ]).…”

“…To estimate the resonant frequency ( f ) of SARS-CoV-2, Manna et al [ 1 ] derived an analytical solution to Lamb’s eigenvalue equation for the first harmonic of the dipolar mode of a sphere (their Equation (1)). Their solution starts by assuming that the ratio between the longitudinal and transverse sound velocities is 2, and uses an approximate expression for the asymptotic value of a Bessel function when its argument approaches zero (their Equation (2)).…”

“…Their solution starts by assuming that the ratio between the longitudinal and transverse sound velocities is 2, and uses an approximate expression for the asymptotic value of a Bessel function when its argument approaches zero (their Equation (2)). Manna et al [ 1 ] used this approximation to replace the spherical Bessel functions in the eigenvalue equation with polynomial functions of the eigenvalues ξ and η (for completeness, we note that the approximation for small arguments of a spherical Bessel functions is: [ 18 ] (p. 708), while their work uses the approximation for cylindrical Bessel functions). However, after performing this substitution, they omitted the multiplication by ξ (which is present in their Equation (1)) from the first term of their Equation (3).…”

“…Following Manna et al [ 1 ], we calculated the resonant frequencies of virus particles from 30 to 70 nm in radius (60 to 140 nm in diameter [ 21 ]), with longitudinal and transverse sound velocities of 1800 m/s and 900 m/s, and estimated that the resonant frequency of SARS-CoV-2 is between 7.4 to 17.2 GHz. Using Equation (5) from Manna et al [ 1 ] with the parameters above provided a frequency range of 12.9 to 30 GHz, although the initial estimate of 6.5 to 16 GHz seems to be based on mistakenly using the virus diameter in place of its radius in Equation (5). In their preliminary experiments, Manna et al [ 1 ] tested inactivation of SARS-CoV-2 with frequencies from 6.5 to 17 GHz, and found that inactivation peaked at 10 GHz.…”