So, please reduce direct social contacts with others and in case they do take place, keep your distance, ensure a high frequency of washing your hands etc. All of these actions should reduce the rate of infection and thereby slow down the spread of the virus. However, more and more people are now asking themselves, how these changes in behaviour actually effect the spread of the virus, as well as the prescribed lock-downs. The following systems model attempts to provide answers to these questions, which Prof. Dr. Hu, of the Universität der Bundeswehr has developed in cooperation with the HORUS ADVISORY GROUP. The model shows the cumulative number of infected people in Germany, since the 01.01.2020 (brown curve), in addition to those people, who are infected, but have not been diagnosed yet in Germany (blue curve). The deciding parameter for the evolution of the pandemic is the rate of infection. The key determining factor for the infection rate is the so called frequency of contact.

Frequency of contact is defined as the number of (norm-) contacts of one person per day, which will lead to an infection with a probability of 1%, in case one of the people is infected with the virus. An example of this could be meeting somebody at a distance of less than 1m. Closer contacts, for example shaking hands increase this probability from 1% to 2% or even more. According to Prof. Dr. med. Christian Drosten, the probability of infection of a doctor lies at 5% during a 15 minute consultation. This is the equivalent of 5 (norm-) contacts for every patient consultation.

Based upon the report bout infections in Germany, we can derive, that the reate of infection until the 16th of March 2020 was at a rate of 18%. In other words, on average, every German had 18 contacts per day with a probability of infection of 1%. During the carnival season, this rate of infection even increased to 26 per day, due to the closer proximity of the people and the higher frequency of contact. Without a change in behaviour, the pandemic would spread exponentially beyond the 31st of May of 2020.