COVID-19 Scientific Advisory Group Rapid Evidence Report Key Research Question: Has there been documented transmission of SARS-CoV-2 virus (or similar viruses) through Heating, Ventilation, and Air Conditioning (HVAC) systems in hospitals or non- hospital settings? Key Messages from the Evidence Summary • There is no clear evidence to date of transmission of SARS-CoV-2 associated with HVAC systems in hospitals or health care facilities, although there is a mechanistic possibility of this occurring. Studies that have identified the presence of viral RNA in procedure generated aerosols have not demonstrated viable virus that would be capable of infecting susceptible hosts, however viral culture may be relatively insensitive. • There is epidemiologic evidence that HVAC conditions may have contributed to transmission of SARSCOV-2 in community settings including a restaurant, call centre and airplane, though in these events spread through close contact was not ruled out, and longer distance localized droplet spread related to airflow (given proximity to the index cases) is more likely than classic airborne transmission. • The need to assess HVAC systems in the control of SARS-CoV-2 and other viruses is highlighted by various interim guidelines (Saran et al., 2020). Notably, rooms with higher air exchanges tend to have less viral RNA detected in the air, based on the literature identified. • Given the complexity in the transmission modalities of SARS-CoV-2 and other similar viruses, lack of data on viable virus in air samples, and the wide variety of HVAC systems, studies have not been able to consider and evaluate all HVAC configurations and their potential to affect transmission of infection. © 2020, Alberta Health Services, COVID-19 Scientific Advisory Group June 5, 2020 11.205 Context • Respiratory viruses are believed to transmit over multiple routes and the relative significance between aerosol and droplet transmission may vary among pathogens. • The Public Health Agency of Canada (2020) and the World Health Organization (2020) consider the route of human-to-human transmission of SARS-CoV-2 to be predominantly via respiratory droplets or contact during close and unprotected contact, with a recommendation to use N95 respirators only in the context of aerosolgenerating medical procedures. • A reported outbreak of COVID-19 in an air-conditioned restaurant in Guangzhou, China that involved three family clusters was attributed to a longer range of droplet transmission, with the authors suggesting that was related to airflow generated by air conditioned ventilation but uncertainty over means of transmission remained. • University of Alberta researchers have received research funding from the Canadian Institutes for Health Research to examine how SARS-CoV-2 may be transmitted through airborne fine particles, and how its movement is controlled by current HVAC designs in non-healthcare settings. • There is concern about the possibility of promoting transmission of SARS-CoV-2 through HVAC systems inside and outside hospital settings. • Evaluating the relative contribution of airborne versus droplet and contact transmission of SARS-CoV-2 is beyond the scope of this review. However, this review is presented under the working assumption that SARS-CoV-2 is primarily transmitted through respiratory droplets or contact and potentially short-range aerosols. • Standards exist for the construction and maintenance of HVAC systems in healthcare and other settings, therefore recommendations for HVAC system design are beyond the scope of this review.
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