“Airborne route and bad use of ventilation systems as non-negligible factors in SARS-CoV-2 transmission” G. Correia, L. Rodrigues et al. 2020. Medical Hypotheses Volume 141, August 2020, 109781
The world is facing a pandemic of unseen proportions caused by a corona virus named SARS-CoV-2 with unprecedent worldwide measures being taken to tackle its contagion. Person-to-person transmission is accepted but WHO only considers aerosol transmission when procedures or support treatments that produce aerosol are performed. Transmission mechanisms are not fully understood and there is evidence for an airborne route to be considered, as the virus remains viable in aerosols for at least 3 h and that mask usage was the best intervention to prevent infection. Heating, Ventilation and Air Conditioning Systems (HVAC) are used as a primary infection disease control measure. However, if not correctly used, they may contribute to the transmission/spreading of airborne diseases as proposed in the past for SARS. The authors believe that airborne transmission is possible and that HVAC systems when not adequately used may contribute to the transmission of the virus, as suggested by descriptions from Japan, Germany, and the Diamond Princess Cruise Ship. Previous SARS outbreaks reported at Amoy Gardens, Emergency Rooms and Hotels, also suggested an airborne transmission. Further studies are warranted to confirm our hypotheses but the assumption of such way of transmission would cause a major shift in measures recommended to prevent infection such as the disseminated use of masks and structural changes to hospital and other facilities with HVAC systems.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7182754/
https://pubmed.ncbi.nlm.nih.gov/32361528/
Keywords: Aerosol; COVID-19; HVAC; SARS-Cov-2; Ventilation.
QUOTES:
“we propose three hypothetic ways in which HVAC systems can contribute to virus transmission:
A) Through air circulation in confined compartments with infected patients;
Production of infectious droplets and subsequent spread to surrounding environment is determined by generation and annihilation processes and may be affected by many variables such as air temperature, relative humidity and ventilation rate (VR). Thus, airborne particles that diffuse can be carried by air movements due to ventilation systems. Still, there is no definite consensus about the ideal VR .
Sanitary facilities must also be addressed as a major factor of virus propagation, since it has been proven that the virus is excreted on urine and feces and sanitary facilities ventilation systems are potentially quite sensitive for the possible propagation of SARS-CoV-2.
B) Through recirculating air in building ventilation systems;
This type of propagation depends on the characteristics of settings and air circuits for HVAC systems. This is a possible mechanism by the which the virus can spread to different floors or to different compartments on the same floor.
C) Every HVAC system comprises a pool of recirculating air to allow for systematic renovation of that air by exchanges with air outside the building. Usually these units are placed on top of the buildings and can be a potential threat to the environment surrounding healthcare facilities. Although posing a smaller probability for transmission, we believe this hypothesis should be addressed in case adequate exhaust filtering systems are not mounted.
NOTES:
Published online 2020 Apr 25.