Detection of SARS-CoV-2 RNA on contact surfaces within shared sanitation facilities

Abstract

Contamination of contact surfaces with SARS-CoV-2 has been reported as a potential route for the transmission of COVID-19. This could be a major issue in developing countries where access to basic sanitation is poor, leading to the sharing of toilet facilities. In this study, we report SARS-CoV-2 contamination of key contact surfaces in shared toilets and the probabilistic risks of COVID-19 infections based on detection and quantification of the nucleic acid on the surfaces. We observed that 54-69% of the contact surfaces were contaminated, with SARS-CoV-2 loads ranging from 28.1 to 132.7 gene copies per cm². Toilet seats had the highest contamination, which could be attributed to shedding of the virus in feces and urine. We observed a significant reduction in viral loads on the contaminated surfaces after cleaning, showing the potential of effective cleaning on the reduction of contamination. The pattern of contamination indicates that the most contaminated surfaces are those that are either commonly touched by users of the shared toilets or easily contaminated with feces and urine. These surfaces were the toilet seats, cistern handles and tap handles. The likelihood (probability) of infection with COVID-19 on these surfaces was highest on the toilet seat (1.76 × 10^-4(1.58 × 10^-6)) for one time use of the toilet. These findings highlight the potential risks for COVID-19 infections in the event that intact infectious viral particles are deposited on these contact surfaces. Therefore, this study shows that shared toilet facilities in densely populated areas could lead to an increase in risks of COVID-19 infections. This calls for the implementation of risk reduction measures, such as regular washing of hands with soap, strict adherence to wearing face masks, and effective and regular cleaning of shared facilities.

Keywords: COVID-19; Contact surface contamination; Digital droplet PCR; Risk assessment; SARS-CoV-2; Shared sanitation.

Fig. 1

Key contact surface areas within the internal surfaces of CABs that were considered in this study.

Fig. 2

Scenario for assessing the exposure and possible risks associated with contamination of the contact surfaces (Adapted from Ryan et al., 2014).

Fig. 3

Percentage of contact surfaces contaminated with SARS-CoV-2 (n = 16).

Fig. 4

Concentration of SARS-CoV-2 on key contact surfaces in the shared toilets (n = 16). *Error bars representing standard deviation.

Fig. 5

Difference in the detection and quantification of SARS-CoV-2 via direct analysis and RNA extraction (n = 16): (A) comparison on prevalence and (B) viral loads. *Error bars representing standard deviation.

Fig. 6

Sensitivity ranking of the infection risks calculation input parameters for exposure to the uncleaned toilet seat.