Novel Coronavirus (COVID-19) Outbreak: A Review of the Current Literature and Built Environment Considerations to Reduce Transmission

1 Biology and the Built Environment Center, University of Oregon, Eugene, OR, 97403 2 Genome Center, University of California Davis, Davis, California 95616 3 Institute for Health and the Built Environment, University of Oregon, Portland, OR, 97209 4 Department of Evolution and Ecology; Department of Medical Microbiology and Immunology; Genome Center, University of California Davis Davis, California 95616 + These authors contributed equally to this work Corresponding author: Patrick F. Horve, pfh@uoregon.edu, (541) 346-5647, Biology and the Built Environment Center, University of Oregon, 5231 University of Oregon, Eugene, OR, 97403-523 Author Contributions: PFH, LD, and KVDW conceived of the scope of the article. LD and PFH wrote the article, with significant writing contributions from DC and MF. PFH developed and created figure 1. PFH, with outside help, created figures 2 and 3. KVDW and JE provided significant edits. All authors reviewed the final manuscript. Acknowledgements: The authors would like to thank Jason Stenson and Cassandra Moseley for comments on the manuscript. The authors would like to thank Paul Ward for his graphical contributions. Preprints (www.preprints.org) | NOT PEER-REVIEWED | Posted: 20 March 2020 doi:10.20944/preprints202003.0197.v2


Introduction
Increased spread of SARS-CoV-2 causing COVID-19 infections worldwide has brought increased attention and fears surrounding the prevention and control of SAR-CoV-2 from both the scientific community and the general public. While many of the precautions typical for halting the spread of respiratory viruses are being implemented, other less understood transmission pathways should also be considered and addressed to reduce further spread.
Environmentally mediated pathways for infection by other pathogens have been a concern in buildings for decades, most notably in hospitals. Substantial research into the presence, abundance, diversity, function, and transmission of microorganisms in the BE has taken place in recent years. This work has revealed common pathogen exchange pathways and mechanisms that could lend insights into potential methods to mediate the spread of SARS-CoV-2 through BE mediated pathways.
Coronaviruses (CoVs) most commonly cause mild illness; but have occasionally, in recent years, led to major outbreaks of human disease. Typically, mutations that cause structural changes in the coronavirus spike (S) glycoprotein enable binding to new receptor types and permit the jump from an animal host to a human host (1) (called "zoonotic" transmission) and can increase the risk of large-scale outbreaks or epidemics (2). In 2002, a novel CoV, severe acute respiratory virus (SARS), was discovered in the Guangdong Province of China (3). SARS is a zoonotic CoV that originated in bats and resulted in symptoms of persistent fever, chills/rigor, myalgia, malaise, dry cough, headache, and dyspnea in humans (4). SARS had a mortality rate of 10% and was transmitted to 8000 people during an 8-month outbreak in 2002-2003 (5). Approximately ten years after SARS, another novel, highly pathogenic CoV, known as middle east respiratory 4 syndrome coronavirus (MERS-CoV), emerged and is also believed to have originated from bats, with camels as the reservoir host (6). MERS-CoV was first characterized in the Arabian Peninsula and spread to 27 countries, having a 35.6% mortality rate in 2220 cases (7).

Coronavirus Disease 2019 (COVID-19)
In December 2019, SARS-CoV-2, a novel CoV, was identified in the City of Wuhan, Hubei Province, a major transport hub of central China. The earliest COVID-19 cases were linked to a large seafood market in Wuhan, initially suggesting a direct food source transmission pathway (8). Since that time, we have learned that person-to-person transmission is one of the main mechanisms of COVID-19 spread (9). In the months since the identification of the initial cases, COVID-19 has spread to 171 countries and territories and there are approximately 215,546 confirmed cases (as of 18 March 2020). The modes of transmission have been identified as hostto-human and human-to-human. There is preliminary evidence that environmentally mediated transmission may be possible; specifically, that COVID-19 patients could be acquiring the virus through contact with abiotic BE surfaces (10, 11). .

Epidemiology of SARS-CoV-2
The Betacoronavirus SARS-CoV-2 is a single-stranded positive-sense enveloped RNA virus (++ssRNA) with a genome that is approximately 30 kilobases in length (15,16). Spike glycoproteins, the club-like extensions projecting from the cell surface, facilitate the transfer of viral genetic material into a host cell by adhesion (12, 13) ( Fig. 1   Previously, it has been confirmed that SARS can be, and is most often, transmitted through droplets (47). Considering that SARS-CoV-2 is from a sister clade to the 2002 SARS virus (48) that is known to transmit from person-to-person, the high incidence of observed person-to-person transmission, and the rapid spread of COVID-19 throughout the world and communities, it is accepted at this time that SARS-CoV-2 can also be spread through droplets (16,49). such as SARS-CoV-2 (53). Furthermore, no filter system is perfect. Recently, it has been found that gaps in the edges of filters in hospitals has been a contributing factor of the failure of filtering systems to eliminate pathogens from the shared air environment (54).
In recent years, the sharing economy has created environments and added new components to how multiple people share the same spaces. It is possible that infectious disease transmission may be impacted by this shift to the sharing economy. Shared workspaces such as co-work environments, rooms in homes, cars, bikes, and other elements of the BE may increase the potential for environmentally mediated pathways of exposure and add complexity to enacting social distancing measures. For example, in cases where alternate modes of transportation were previously single occupancy vehicles, these trips are now often replaced with rideshare programs or transportation network companies, the potential for exposure may increase.

Control and Mitigation Efforts in the BE
The spread of COVID-19 is a rapidly developing situation, but there are steps that can be taken, Enacting enhanced building HVAC operational practices can also reduce the potential for spread of SARS-CoV-2. Even though viral particles are too small to be contained by even the best HEPA and MERV filters, ventilation precautions can be taken to ensure the minimization of  decrease connectivity. Space syntax analysis demonstrates a relationship between spatial disposition and degrees of connectivity (Fig 3) and has been shown to correlate with the abundance and diversity of microbes within a given space (93). Understanding these spatial concepts could be part of the decision-making process of whether to implement social-distancing measures, to what extent to limit occupant density, and for how long to implement the measures. The same negative pressure that aids in preventing spread of aerosolized pathogens from inside the room can involuntarily expose the room occupants to airborne pathogens that are sourced

Conclusion
The number of individuals who have contracted COVID-19 or have been exposed to SARS-