# Covid : in the city or in the countryside, assess the risk of meeting an infected person - The Point

Difficult not to ask the question when entering a restaurant, in a store or in an office : how many people are potentially contaminated around us ? Each one can

Difficult not to ask the question when entering a restaurant, in a store or in an office : how many people are potentially contaminated around us ? Each one can now estimate this risk according to the place where it is located and the number of people around him. The site CovidTracker, created and hosted by a young computer engineer has just put online a tool as simple as it is relevant to take the measure of the movement of the virus around itself. This simulation, developed with Elias, Orphan, can be useful, while the number of new cases is breaking records, with more than 52,000 infections in 24 hours announced Sunday, October 25.

By a simple calculation of probability, this simulator allows to make the link between an incidence rate (the number of infected people for 100,000 inhabitants) and a number of people cross at a time instant T. " let's Take a theoretical example, offers the young founder of the site, William Rozier, in a wedding of 200 people which would take place in Saint-Étienne, where the incidence rate is currently 1 020, the risk of meeting a positive person among the guests would be 87 %. If you are invited to a student party in Paris, we can also use incidence rates, available by age group. Thus, in this last example, in which a private party that would bring together 30 students from the capital, there would be a chance on five to fall on a guest Covid+. "With this tool, one can well understand why the protests are limited and why, in some places, it is better to avoid them to the maximum.

The tool CovidTracker can measure the movement of the virus around itself. © DR

To make his small calculation in CovidTracker, so you have to go pick up the incidence of your department or of your town, the official data available on the public Health website France. They are compiled from the results of tests carried out in the laboratories. You can also use the map published on Wednesday 21 October on the website of the agency, it offers a level of detail never achieved so far in the publication of data relating to the epidemic of Covid-19. It allows you to view the incidence rate by area of residence of 4 000 inhabitants, and gives, by example, a precise idea of the presence of the virus by neighborhood in large cities.

Read also Covid-19 : how the epidemic has exploded in less than a month

But be careful not to confuse a passage from the site CovidTracker will not allow you to measure the risk of being infected participating in an event such as a meal or a meeting. In fact, the rudimentary calculation does not take into account, for example, gestures barriers that each not or not adopt it at this exact moment or even the time spent in close proximity to each other.

It does not tell you if you have really crossed a infected person in the preceding days, that it is the job of the application tracing of the government TousAntiCovid. No, it is to visualize a probability of crossing to a specific moment a person who is infected or ill in a department in a municipality or in an area depending on the size of the group of individuals around you. Limited ? Perhaps, but the benefit of grasp of a single glance, such a risk is not less striking at a time when extensions of the curfew are discussed and reconfinements already mentioned.

Consult our folder : Covid : the time of the second wave