The Role of the Built Environment in COVID-19 Transmission
Above: Disinfecting subway cars during the 2019-2020 Coronavirus pandemic. Source: Wikipedia.
Article: Dietz, L.; Horve, P.F.; Coil, D.; Fretz, M.; Van Den Wymelenberg, K. 2019 Novel Coronavirus (COVID-19) Outbreak: A Review of the Current Literature and Built Environment (BE) Considerations to Reduce Transmission. Preprints 2020, 2020030197 (doi: 10.20944/preprints202003.0197.v1).
The world is in the midst of a full-blown pandemic, with over 200,000 cases of COVID-19 in over 170 countries. To date, more than 8200 have died. Entire countries are on lockdown, with borders sealed and citizens ordered to stay home.
For the time being, COVID-19 is not going away, as new cases and more deaths are recorded every day.
In an effort to curb its spread, all aspects of COVID-19 are currently under study. The viral structure of the COVID-19 virus has been studied. Vaccines to prevent COVID-19 are under development, as are medications to treat COVID-19 infection. The transmission of COVID-19 from person to person is known (as of now) to happen via droplets of fluid containing the virus spread by coughing and sneezing.
Research is also under way into how the built environment (anything built by humans) affects COVID-19 transmission. A manuscript in process of publication (and currently available via Preprints) offers an overview of the current knowledge about the built environment’s effects on the transmission of COVID-19 and similar viruses.
The built environment includes cars, roads, buildings, homes, other man-made spaces and literally anything else man-made. In today’s world, most humans spend the vast majority of their time in close contact with some aspect of the built environment.
For the transmission of COVID-19, and other transmissible diseases in general, the built environment functions as fomites, or spaces outside the human body where the virus particles can temporarily exist before entering another human body. For example, imagine a person infected with COVID-19 sat at a table and sneezes, and liquid droplets (containing COVID-19 virus particles) from that sneeze lands on the table. That table is now a fomite. After that person leaves, another person can sit at the same table, come into contact with the virus-containing droplets, and also become infected. Of note, COVID-19 has been shown to survive up to 72 hours on some surfaces.
Figure 2 from the manuscript in progress, shown below, illustrates all the various areas in a typical kitchen that can harbor COVID-19 particles after contact with an infected person. Area a shows the virus particles within the body of the infected person, area b shows areas that can become fomites through coughing or sneezing, and area c shows hands and fingers that can harbor virus particles after wiping the nose or mouth, and area d shows areas that can become fomites after being touched with the hands and fingers from area c.
The transmissibility of a particular disease is denoted by its R0 (pronounced R-naught), which is a measure of how many non-infected (or susceptible) people can become infected after contact with one person. For example, measles has an R0 of 12-18. This means that the one person infected with measles can infect 12-18 others through contact.
The R0 of COVID-19, from currently available data, is estimated to be 1.5-3. However, in highly crowded areas, COVID-19 seems to be far more transmissible than those numbers suggest. An example presented by the researchers is the Diamond Princess cruise ship, quarantined in Yokohama, Japan. Of the 3,700 people on board, 712 tested positive for the virus. This suggests that crowded areas and confirmed spaces bring about a far higher R0 for COVID-19.
Architectural preferences, such as large open office spaces with many desks – as opposed to small, enclosed private offices – can also foster COVID-19 transmission by increasing the number of people sharing the same space without walls to separate them. This can be exacerbated even more if the heating, venting, and air condition (HVAC) systems are somehow contaminated by COVID-19 particles. This is true in other enclosed spaces like airplanes, also.
The overall goal of controlling a pandemic like the current COVID-19 outbreak is to reduce the number of cases over a given time period to a level that the healthcare system can adequately handle. This is known as flattening the curve, referring to the epidemic curve that tracks the number of cases in an outbreak. The figures below show this visually.
The current social distancing measures being enacted worldwide are aimed to reduce the instances of crowds. This will help avoid scenarios like the Diamond Princess. Offices and other business temporarily closing or switching to remote working is mitigating the transmission risks inherent when many people share a single space, no matter small or large. These risks could be further mitigated by ensuring that HVAC systems are equipped effective filtration systems (that are properly maintained).
Disinfection by ethanol has been shown to be effective and has been heavily used for decontamination during the current pandemic. This should obviously continue, both for potential fomites, general areas, and also for personal hand hygiene, especially after coughing or sneezing (covering the mouth and nose is preferable than sneezing or coughing into the air or other surfaces).
The current COVID-19 outbreak is a dynamic and unprecedented situation. The most important objective currently is to slow the spread of the disease and to treat those that are already infected. While healthcare personnel are working tirelessly on the treatment front, it falls to all of us to do our part in helping stem this surging pandemic tide. Practicing good hand hygiene, social distancing (including personal isolation if suspected or symptomatic of COVID-19 infection), and proper disinfection can go a long way in ensuring that our built environment is a source of shelter and comfort – and not yet another avenue for COVID-19 infection.
More information about COVID-19 is available from the Centers for Disease Control and Prevention (CDC), the World Health Organization (WHO), and your local health authorities.