Corona outbreak – why isolation of infected people matters

Just hacked a simple simulation on the spread and effects of a virus, like the Corona virus that is in voque as we speak.

The model is very simple, with the following assumptions/constants:

• The population size is constant, in the example, 160.000 people
• The initial probability for anyone within the population to be infected is 0.001
• The period during which a person carrying the virus is able to infect others is 2 weeks
• the probability that a person carrying the virus will infect another person when they meet is 0.05

start by looking at what happens when the average number of contacts per week per person is 40:

We can see that the process is very fast – already during the second week, the number of people infected is almost 140.000, out of total population of 160.000

Next, let’s look at mortality: with a mortality rate of 2%, the process results in about 2700 deceased, very early in the process.

Now let’s look at what happens if we limit the number of contacts to 5:

Mortality after limiting number of contacts drops by two orders of magnitude, from about 1500 to 10.

Finally, let’s look at what happens if we increase the period during which an infected person can contaminate others from 2 weeks to 5 weeks, while keeping the number of contacts constant at 5:  here, the max number of people infected is about 3000, that is, an order of magnitude greater than when the contamination period was 2 weeks, and the process peaks much later, after 17-18 weeks instead of already during week 2.

 

Now, mortality also increases massively, from the previous 10, to almost 700.

Lesson learned – at least as given by the parameters and constraints of this simulation run: limiting the amount of physical contact between people, and trying to reduce the contamination period are both key tools for containing a virus outbreak.

[Addendum] Below a graphical representation of the spreading of virus :

Further reading on spread of virus