Published: Mar 2020 | DOI: 10.1128/mSystems.00245-20

2019 Novel Coronavirus Outbreak: A Review of the Current Literature and Built Environment Considerations to Reduce Transmission

Dietz, L. | Horve, P.F. | Coil, D. | Fretz, M. | Van Den Wymelenberg, K.


The authors of this study reviewed the substantial research carried out over the last decade into the microbiology of the built environment (BE) and the known information about SARS-CoV-2. The objective was to provide actionable and achieveable guidance to BE decision makers, building operators and all indoor occupants attempting to minimize infectious disease transmission.

HVAC operational practises to reduce the spread of SARS-CoV-2

It has been confirmed that SARS can be, and is most often, transmitted through droplets. Considering that SARS-CoV-2 is from a sister clade to the 2002 SARS virus, 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, it is generally accepted at this time that SARS-CoV-2 can also be spread through droplets.

Based upon previous investigation into SARS, spread through aerosolization remains a potential secondary transmission method, especially within the BE that contain heating, ventilation, and air conditioning (HVAC) units.

    • Higher outside air fractions and higher air exchange rates in buildings may help to dilute the indoor contaminants that are breathed within the BE. Higher outside air fractions may be possible by increasing ventilation damper positions on air-handling units, thus exhausting a higher ratio of indoor air and any airborne viral particles present. For buildings without central HVAC systems, simply opening windows, when outdoor temperatures allow, will increase air exchange.
    • Maintaining an indoor relative humidity between 40%-60% may help to limit the spread and survival of SARS-CoV-2 within the BE. Concurrently it maintains hydrated and intact mucosal barriers of human occupants, resulting in an increase resistance against any microbial attack.
    • Light is another mitigation strategy for controlling the viability of some infectious agents indoors. Building operators should encourage blinds and shades to be opened, to admit abundant daylight and sunlight. Implementing targeted UVGI treatment may be prudent in spaces where individuals that tested positive for COVID-19 were known occupants.

    Personal hygiene practises to reduce the spread of SARS-CoV-2

    • Proper handwashing is a critical component of controlling the spread of SARS-CoV-2, other coronaviruses, and many respiratory infections.
    • Individuals should avoid contact and spatial proximity with infected persons.
    • Properly applied hand sanitizer may be a valuable tool against the spread of SARS-CoV-2 in the BE.
    • Items should be removed from sink areas to ensure aerosolized water droplets do not carry viral particles onto commonly used items, and countertops around sinks should be cleaned using bleach or an alcohol-based cleaner on a regular basis.

    Administrators and building operators should post signage about the effectiveness of handwashing for at least 20 seconds with soap and hot water, ensure soap dispensers are full, provide access to alcohol-based hand sanitizer, and implement routine surface cleaning protocols to high touch surfaces where contamination risks are high, such as around sinks and toilets.

      Scientific studies main menu 

      Doc's view...

      by Walter Hugentobler

      This literature review gives valuable information for building operators on actions they can take to mitigate the spread of COVID-19.

      Alongside the regular advice we hear from governments on hand washing and social distancing, its finding show that increasing air exchange rate, maintaining indoor humidity at 40-60%RH (not achievable in winter without active humidification) and increasing natural light can all play a positive role.

      The scientific studies referenced in this literature review provide valuable insight into how we can create a healthier built environment, not just at a time of crisis but in our everyday lives. For instance, if hospitals and public places kept their indoor humidity at the recommended 40-60%RH, many lives would be saved every year from reduced 'flu transmission alone.

      Other scientific studies relating to humidity and health