There has been increasing evidence that COVID-19 is being transmitted indoors through air handling (A/C) systems. This has prompted some states to only allow businesses to open outside locations (restaurants, hair salons, etc.). Below is some information from a wide variety of sources.
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New York Gov. Andrew Cuomo to announce on July 9 that malls in the state would be required to install MERV-13 filters in any HVAC system that can use them before reopening.
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Aerosol and surface contamination of SARS-CoV-2 observed in quarantine and isolation care
The University of Nebraska Medical Center (UNMC), with its clinical partner Nebraska Medicine, cared for 13 individuals with confirmed SARS-CoV-2 infection evacuated from the Diamond Princess cruise ship as of March 6th, 2020.
Results
Overall, 70.6% of all personal items sampled were determined to be positive for SARS-CoV-2 by PCR (Fig. 1B and Table S1). Of these samples, 75.0% of the miscellaneous personal items (described in the “Methods” section) were positive by PCR, with a mean concentration of 0.22 copies/µL. Samples of cellular phones were 77.8% positive for viral RNA (0.17 copies/µL mean concentration) and remote controls for in-room televisions were 55.6% percent positive (mean of 0.22 copies/µL). Samples of the toilets in the room were 81.0% positive, with a mean concentration of 0.25 copies/µL. Of all room surfaces sampled (Fig. 1B and Table S1), 75.0% were positive for SARS-CoV-2 RNA. 70.8% of the bedside tables and bed rails indicated the presence of viral RNA (mean concentration 0.26 copies/µL), as did 72.7% of the window ledges (mean concentration 0.22 copies/µL) sampled in each room. The floor beneath patients’ beds and the ventilation grates in the NBU were also sampled. All five floor samples, as well as 4 of the 5 ventilation grate samples tested positive by RT-PCR, with mean concentrations of 0.45 and 0.82 copies/µL, respectively.
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https://www.webmd.com/lung/news/20200708/air-conditioning-may-be-spreading-covid
In another study, which hasn’t yet been peer reviewed, researchers swabbed three different HVAC units at the Oregon Health and Science University Hospital in Portland. Then they checked their samples for the presence of genetic material from the SARS-CoV-2 virus. The swabs were positive in 1 out of every 4 samples taken. “We found it in multiple locations within the air handler,” says study author Kevin Van Den Wymelenberg, PhD, a professor of architecture and director of the Institute for Health in the Built Environment at the University of Oregon in Eugene.
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https://www.cdc.gov/mmwr/volumes/69/wr/mm6919e6.htm
High SARS-CoV-2 Attack Rate Following Exposure at a Choir Practice — Skagit County, Washington, March 2020
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Cluster of Coronavirus Disease Associated with Fitness Dance Classes, South Korea
https://wwwnc.cdc.gov/eid/article/26/8/20-0633-f1
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It is Time to Address Airborne Transmission of COVID-19
https://academic.oup.com/cid/advance-article/doi/10.1093/cid/ciaa939/5867798
239 Scientists requested the World Health Organization to start warning people that COVID-19 is airborne.
Commentary
We appeal to the medical community and to the relevant national and international bodies to recognize the potential for airborne spread of COVID-19. There is significant potential for inhalation exposure to viruses in microscopic respiratory droplets (microdroplets) at short to medium distances (up to several meters, or room scale), and we are advocating for the use of preventive measures to mitigate this route of airborne transmission. Studies by the signatories and other scientists have demonstrated beyond any reasonable doubt that viruses are released during exhalation, talking, and coughing in microdroplets small enough to remain aloft in air and pose a risk of exposure at distances beyond 1 to 2 m from an infected individual (see e.g. [1-4]). For example, at typical indoor air velocities [5], a 5 μm droplet will travel tens of meters, much greater than the scale of a typical room, while settling from a height of 1.5 m to the floor. Several retrospective studies conducted after the SARS-CoV-1 epidemic demonstrated that airborne transmission was the most likely mechanism explaining the spatial pattern of infections.
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https://www.washingtonpost.com/health/2020/07/18/coronavirus-superspreading-events-drive-pandemic/
Harper’s Restaurant and Brew Pub in East Lansing closed June 20 after the outbreak
Investigators were told there were 225 customers on two floors with a normal capacity of 950. The air conditioning was on, and some people were out on a deck. Of the 187 total cases traced back to Harper’s Restaurant as of Friday, 144 were among people who had been at the venue.
Jose-Luis Jimenez, a researcher at the University of Colorado Boulder, was one of 239 scientists who penned an open letter to the WHO, calling for greater recognition of the role that clouds of fine aerosols containing the virus may play in its spread, prompting the agency last week to acknowledge “emerging evidence” of airborne transmission. “It is becoming clear that the pandemic is driven by superspreading events, and that the best explanation for many of those events is aerosol transmission.” Jimenez said.
Harper’s said in a Facebook post that it is working to modify its heating and air conditioning system with air purifying technology.
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Ramon Padilla, and Javier Zarracina, USA TODAY Updated 11:00 a.m. PDT July 17, 2020
The WHO says that airborne transmission can occur during medical procedures that generate aerosols and has been actively evaluating whether the virus may also spread through aerosols in indoor settings with poor ventilation.
Dr. Julian W. Tang, Associate Professor at the University of Leicester, United Kingdom, encourages the WHO to go a step further with its recommendations. "You cannot separate out droplet and fine aerosol emissions in everyday activities like talking, breathing and laughing.” Many scientists believe droplets and aerosols are on a continuum of sizes. “So if they accept that droplet transmission is happening they cannot exclude any contribution from aerosols."
"Aerosols are different," says Dr. Stanley Deresinski, clinical professor of medicine and infectious diseases at Stanford University. "Very small particles may be suspended in the air for a long time, sometimes for hours. They're suspended by air currents."
Those floating airborne droplets — some shielded by turbulent gas clouds — can stay suspended long enough for someone to walk through and inhale the virus.
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