How do we assess the risks in our daily lives?
Text updated on 2020-09-19
The COVID-19 epidemic makes us reconsider our daily life from a new angle: how to limit the risks of SARS-CoV-2 coronavirus infection? To help you assess the risks in our daily lives, we offer you an easy-to-use risk scale and a questionnaire to evaluate the risk of infection in everyday situations.
Contamination by the SARS-CoV-2 coronavirus depends on several parameters:
- Ventilation: the more a place is aired and ventilated, the lower the risk of infection.
- Mask: The mask is a filter that works both ways. It reduces the transmission of particles from SARS-CoV-2. The more the mask is worn, the lower the risk.
- Activity: the amount of emission per droplet and aerosol from SARS-CoV-2 depends on the activity. Speaking loudly, singing or being out of breath causes more droplets and aerosols to be emitted than whispering or closing your mouth. The louder the activity, the greater the risk.
- Distance: the greater the distance between individuals, the lower the risk.
- Density: the higher the number of people, the higher the risk.
- Duration: the longer the activity lasts, the higher the risk.
The risk of contamination increases in areas where the COVID-19 epidemic is active (i.e., many cases of patients with COVID-19). In addition to the risk of contamination, there is also the risk of developing a severe form of COVID-19 . The risk is not the same for a 10-year-old child as for a 70-year-old person. For vulnerable people or those who frequent vulnerable people, caution is advised.
Infection risk scale
To get an idea of the risk of being infected with the SARS-CoV-2 coronavirus or of infecting someone, we propose a scale from 0 to 4 which illustrates different situations in everyday life, from the least risky (risk = 0) to the most risky (risk = 4).
To illustrate the risk scale, here are some typical situations that will help represent the different levels:
Risk level 0
- alone: at home, in nature, in the car, by bike...
- walking in the wild with someone, all masked with a distance of more than one meter.
- secluded beach
Level 1 risk
- walking in the wild with someone, without a mask and a distance of more than one meter
- home shopping delivery
- mask museum
- municipal outdoor swimming pool, distance of more than one meter
- open-air market with mask and non-accessible stalls
- remote outdoor sports (tennis, skiing, etc.)
Risk level 2
- public transport (bus, train, subway, tram) with a mask and a distance of more than one meter
- in nature with several people without masks and a distance which is sometimes less than one meter
- eating outdoors, distance of one meter between people
- cafe terrace
- covered market with mask and non-accessible displays
- Indoor distance sports (tennis, etc.)
- ski resort
- indoor municipal pool
- busy beach
- working at the office, with a mask and a distance of one meter between people
Level 3 risk
- sharing objects without precaution (computers, telephones, pens, microphones, etc.) and touching one's face
- eating indoors at a distance of more than one meter
- weight/exercise room with a distance of more than one meter
- places frequented by less than 500 people with masks and a distance of more than one meter (concerts, cinemas, etc.)
- school, college, high school, university with mask
Level 4 risk
- all places frequented by more than 500 people: concerts, shows, festivals, stadiums, events, etc.
- karaoke and disco
- chorus or choir
- cocktails and parties, peanuts and chips to share
- public transport without a mask, without a distance of more than one meter
- races in a crowded enclosed area without a mask, without a distance of more than one meter
- contact sport (boxing, etc.) and contact sport (basketball, handball, etc.) without a mask
- long haul flight without a mask or with a poorly fitted mask
To assess the risk of infection for a particular life situation, answer the questions in this QUESTIONNAIRE!
In conclusion, for risk management, it is up to each individual to decide what risks he or she takes, within the framework allowed by law. Those who are vulnerable, or who are in contact with vulnerable people, will have to be particularly careful: be careful of high-risk activities. Finally, even if one does not fear much for oneself, caution is necessary to protect others and limit the spread of the epidemic as much as possible.
Disclaimer: The creation of the scale and the choice of situations illustrating each level of risk were based on the results of a survey carried out in June 2020 with 11 scientists involved in an active literature review on the COVID-19. Various everyday situations were assessed via 50 questions using a risk scale ranging from 0 to 4. The score associated with each situation is that estimated by at least 75% of the scientists in the group. This risk scale as well as the risk assessment questionnaire are presented for information purposes only and do not constitute medical advice, nor do they engage the responsibility of their authors.
In closed environments the risk of transmission of the SARS-CoV-2 coronavirus is 18.7 times greater than in the open air.Nishiura, H., Oshitani, H., Kobayashi, T., Saito, T., Sunagawa, T., Matsui, T., ... & Suzuki, M. (2020). Closed environments facilitate secondary transmission of coronavirus disease 2019 (COVID-19). medRxiv. PREPRINT
Ventilation in closed environments is one of the important factors in reducing the concentration of SARS-CoV-2 coronavirus.Liu, Y., Ning, Z., Chen, Y., Guo, M., Liu, Y., Gali, N. K., ... & Liu, X. (2020). Aerodynamic analysis of SARS-CoV-2 in two Wuhan hospitals. Nature, 1-4.
In a Chinese air-conditioned restaurant, contamination of the customers occurred in the ventilation flow of the air conditioning system.Lu, J., Gu, J., Li, K., Xu, C., Su, W., Lai, Z., ... & Yang, Z. (2020). COVID-19 outbreak associated with air conditioning in restaurant, Guangzhou, China, 2020. Emerging infectious diseases, 26(7).
The physical distance between people (more than one meter) and masks prevents the transmission of the SARS-COV-2 coronavirus.Chu, D. K., Akl, E. A., Duda, S., Solo, K., Yaacoub, S., Schünemann, H. J., ... & Hajizadeh, A. (2020). Physical distancing, face masks, and eye protection to prevent person-to-person transmission of SARS-CoV-2 andCOVID-19: a systematic review and meta-analysis. The Lancet.
Talking increases aerosol emission and transmission of the SARS-CoV-2 coronavirus in closed environments.Stadnytskyi, V., Bax, C. E., Bax, A., & Anfinrud, P. (2020). The airborne lifetime of small speech droplets and their potential importance in SARS-CoV-2 transmission. Proceedings of the National Academy of Sciences, 117(22), 11875-11877.
The louder we speak, the larger and more numerous the aerosol particles emitted.Asadi, S., Wexler, A. S., Cappa, C. D., Barreda, S., Bouvier, N. M., & Ristenpart, W. D. (2019). Aerosol emission and superemission during human speech increase with voice loudness. Scientific reports, 9(1), 1-10.
Measurement of the stability of the SARS-CoV-2 coronavirus under different environmental conditions.Chin, A., Chu, J., Perera, M., Hui, K., Yen, H. L., Chan, M., ... & Poon, L. (2020). Stability of SARS-CoV-2 in different environmental conditions. The Lancet, 2020.
The choice of the physical distance of 1-2 meters is based on experimental data of droplet and aerosol circulation, which depends on many parameters: ventilation (the more it is ventilated, the faster the particles will disappear), the strength of particle emission (the louder you speak, the more out of breath you get and the higher the particle emission), the exposure time (the longer you stay in a place, the higher the particle concentration). The distance of 1 or 2 meters is an arbitrary estimate that must be re-evaluated according to the different parameters mentioned above. If everyone is out of breath in a poorly ventilated area, a distance of 1 or 2 meters is not sufficient to protect individuals. If no one is talking in a well-ventilated area, one meter may be sufficient.Jones, N. R., Qureshi, Z. U., Temple, R. J., Larwood, J. P., Greenhalgh, T., & Bourouiba, L. (2020). Two meters or one: what is the evidence for physical distancing in covid-19?. bmj, 370.