Inactivation of viruses on surfaces by infrared techniques

Abstract

Several studies on vaccines and medicines against virus-based illnesses (COVID-19, SARS, MERS) are being conducted worldwide. However, virus mutation is an issue. Therefore, inactivation and disinfection of viruses are crucial. This paper presents a method for virus inactivation by physical techniques. The infrared (IR) technique is preferred over other disinfection techniques such as ultraviolet (UV) and chemical disinfectants (alcohol) due to the associated health and environmental benefits. In this study, IR sources with various wavelengths were characterized and a far infrared (FIR) source was used to inactivate viruses. FIR sources have a therapeutic effect on the human body and have been used in medical centers. Virus spread is highly affected by environmental conditions such as temperature, humidity, and airflow. A setup with IR sources, an IR camera, an automatically controlled humidity chamber, and an airflow unit was constructed to study the viability of viruses in stationary droplets as a function of relative humidity and temperature. Bacteriophage Phi6 was used as a model organism for studying enveloped viruses such as influenza and coronavirus. IR techniques were used for studying virus inactivation. The effect of various physical conditions such as temperature, humidity, and airflows was considered to study the effect of radiation on the stationary droplets of Phi6. All measurements were performed under laboratory conditions with controlled temperature and humidity. The IR camera system was used to measure the surface temperature of Phi6 suspension droplets. The samples subjected to IR radiation were processed for plaque assay preparation and counting. Measurements were carried out to reduce and eliminate droplets, which are one of the transmission pathways of viruses. IR was radiated in closed and open-air conditions with appropriate humidity and temperature. This study reports the effective inactivation of viruses by FIR. The inactivation rate under 50 %rh for IR radiated at 1.4 m height for 3 h in closed environmental chamber was 90%, and that under an airflow rate of 0.20 m/s for 10 min in open-air conditions at a height of 1.0 m was 45.7%.

Fig. 1

Experimental setup for measurements in open environment. a) Scaffold system and b) schematic details of the measurement set up.

Fig. 2

Experimental set up for the measurements inside the humidity cabin.

Fig. 3

Images of the formed plaques which represents the lysis of Phi6 infected bacterial cells observed on plates of all dilution levels. In a), b) and c), plaques are too much that can not be counted, in d) and e) plaques are countable, in f) no significant plaques.$ViralTiter\left(PFU/mL\right)=\frac{numberofplaques}{\left(dilutionfactorxvolumeofvirusdilutonadded\right)}$

Fig. 4

Inactivation graph of 100 μL virus containing solution applied for 3 h at a distance of 0.5 m with a FIR source. Error bars indicate the ±10% uncertainty in measurements.

Fig. 5

Graph of the inactivation at different times of FIR application 1 m distance at 80 %rh level (blue columuns) and at 70 rh % level (yellow colums). Measurements were performed inside the cabin. Error bars indicate the ±10% uncertainty in measurements.

Fig. 6

Virus inactivation in different distances and humidity levels.

Fig. 7

Surface temperatures of the virus bacteriophage culture plate during IR application. ±2.0 °C error in surface temperatures measurements should be mentioned.

Fig. 8

Virus inactivation according to different application times of the IR application in ambient conditions.

Fig. 9

Virus inactivation with 0.10 m/s (blue columns) and 0.20 m/s (orange columns) air flow in 10 min, 20 min and 30 min of FIR applications. Error bars indicate the ±10% uncertainty in measurements.

Fig. 10

Time-dependent decrease of 100 mg isotonic droplet under the effect of IR sources and ambient conditions on wooden surfaces. Ambient conditions mean no IR radiation.

Fig. 11

Temperature during the droplet evapoation by IR application.

Fig. 12

Relative humidity during the droplet evapoation by IR application.