Investigating the influences of ventilation on the fate of particles generated by patient and medical staff in operating room

The ongoing outbreak of coronavirus disease 2019 (COVID-19) has spread rapidly on a global scale. Although it is clear that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is transmitted through human respiratory droplets and direct contact, the potential for aerosol transmission is poorly understood1-3. Here we investigated the aerodynamic nature of SARS-CoV-2 by measuring viral RNA in aerosols in different areas of two Wuhan hospitals during the outbreak of COVID-19 in February and March 2020. The concentration of SARS-CoV-2 RNA in aerosols that was detected in isolation wards and ventilated patient rooms was very low, but it was higher in the toilet areas used by the patients. Levels of airborne SARS-CoV-2 RNA in the most public areas was undetectable, except in two areas that were prone to crowding; this increase was possibly due to individuals infected with SARS-CoV-2 in the crowd. We found that some medical staff areas initially had high concentrations of viral RNA with aerosol size distributions that showed peaks in the submicrometre and/or supermicrometre regions; however, these levels were reduced to undetectable levels after implementation of rigorous sanitization procedures. Although we have not established the infectivity of the virus detected in these hospital areas, we propose that SARS-CoV-2 may have the potential to be transmitted through aerosols. Our results indicate that room ventilation, open space, sanitization of protective apparel, and proper use and disinfection of toilet areas can effectively limit the concentration of SARS-CoV-2 RNA in aerosols. Future work should explore the infectivity of aerosolized virus.

The outbreak of atypical pneumonia, referred to as severe acute respiratory syndrome (SARS), has spread to many countries in the world. SARS may infect human bodies by the tiny droplets or particles carrying various virus and bacteria, which are generated by the respiratory system of infected patients. This paper presents the numerical analysis of the influence of generating ways of the droplets or particles on the transport and distribution of the droplets or particles indoors. The drift flux model, which considers the settling of particles or droplets under the effect of gravitational sedimentation, is adopted to simulate the droplets transport and distribution indoors during respiration and sneezing or coughing process, while the simplified model for solving the continuous fluid flow is combined. Two different cases considering the normal respiration and coughing or sneezing are studied, respectively, and two different outlet velocities from the mouth for the sneezing or coughing process are considered. The results show that droplets or particles generated by normal breathing process transport a relatively short distance, while droplets or particles generated during coughing or sneezing may travel much longer distances, which may pose adverse effect on human bodies for defending the SARS or other infectious diseases.