This scientific analysis will try to simulate the virus risk of infection effect on the society across different situations, based on size and density of gatherings/social clusters. This analysis has been conducted specifically for Greece.

What You Should Know

  • - The Risk of Infection is the probability for an individual to be infectious.
  • - Active cases include diagnosed cases, asymptomatic carriers or those that are pre-symptomatic but can still spread the virus (estimated).
  • - The Risk of Infection for an individual is the ratio of the maximum Active cases per period of study, to the Greek population.

Selected Scenarios demonstrating the Risk of Infection in Greece, under variable situations, interpreting our pandemic experience and the ways preventive measures can influence this experience.

Risk vs Gathering size without Masks


We note that the chance of infection in a gathering of 1000 attendees, that do not use masks was the lowest in the summer period (63%), followed by that in the spring (78%) and reached its highest value (100%) in the fall. This is due primarily to the different spread of the virus in the community and secondly to other factors such as the temperature.

Risk by Precautions vs Gathering Size in Spring

No MaskMaskMask & Ventilation0%10%20%30%40%50%60%70%80%90%100%0500100015002000250030003500400045005000

Risk by Precautions vs Gathering Size in Fall

No MaskMaskMask & Ventilation0%10%20%30%40%50%60%70%80%90%100%050010001500200025003000

Comparing the effect of preventive measures in the 1st wave vs the 2nd wave, we note that there is much lower contribution of the measures in the fall. For example, the risk of infection in a gathering of 1000 attendees in the spring decreaces from 78% to 26% with mask usage and ventilation. While in the fall, the chance for risk infection with or without mask is certain and comes down to 86% if proper ventilation exists. This observation suggests that usual precautions are of minor importance, once the spread of the virus is extensive in the community.

Indoor/Outdoor Risk vs Gathering Size in Spring

Outdoor RiskIndoor Risk0%20%40%60%80%100%120%0500100015002000250030003500400045005000

Indoor/Outdoor Risk vs Gathering Size in Fall

Outdoor RiskIndoor Risk0%20%40%60%80%100%120%0500100015002000250030003500400045005000

Comparing the risk of infection in outdoor versus indoor gatherings, we note that there is a big difference in favor of outdoor gatherings. This difference is similar during the 1st and the 2nd wave of the pandemic, with a remarkable increase of the risk of infection, even in outdoor gatherings during the 2nd wave.

Risk by Region vs Gathering Size in Spring


Risk by Region vs Gathering Size in Fall


Comparing the risk of infection between Athens and Thessaloniki, we note that it follows a similar pattern in the 1st wave, while in the 2nd wave, there is a much higher chance of infection in the region of Thessaloniki. This is again a result of the much higher spread of the virus in Thessaloniki, during the 2nd wave.

Risk by Venue vs Mask Usage

MaskNo Mask

This reaviling scenario demonstrates that the risk of infection is much higher in recreation venues such as bars, restaurants and other overcrowding places, while venues we normally visit in our everyday routines (subway, supermarket, parks) are much less dangerous. Needless to mention, the positive effect of mask usage in any of these cases.

Covid-19 vs Car Accident Odds of Death

MaskNo Mask

To demonstrate how risky are our everyday habits during the pandemic, we chose a scenario that compares the chance of dying from covid-19 to the chance to be involved in a fatal car accident. Example given, visiting a bar we are 264 times more prevalent to die from covid-19, compared to our death in a car accident. Again, the mask usage decreases this risk by more than half.

If you have found this small selection of scenarios interesting, you can always contact us for more.