Found an excellent article that explains the whole situation with math.
Feel free to run it through Google translate:
https://www.corriere.it/cronache/20_febbraio_25/matematicadel-contagioche-ci-aiutaa-ragionarein-mezzo-caos-3ddfefc6-5810-11ea-a2d7-f1bec9902bd3.shtmlI'll try to make a very short summary.
Let's apply the "SIR" method, let's divide people into S / I / R categories.
S = Susceptible, people that could be infected.
I = Infected, those who were already hit by the virus.
R = Recovered, people who healed and no longer transmit the virus.
There's also another factor to consider: R0. Which value it is? it's average of people infected by someone who carries the virus. This value for the coronavirus is currently 2,5. Seems low, measles was / is around 15, but wait to be happy.
R0 needs to be below 1 for the infection to die out. If an infected person does not infect another one, the spreading of the disease (yeah, I thought about the song) stops. When R0 is above 1, we have an epidemic.
And now we come to the crucial issue - how long the disease takes to spread. The average time that elapses between when a person is infected, and when this person infects another. The coronavirus' time is measured at about 7 days.
This is why the governments adopted the measures they adopted. This is why Lombardy, the region in Italy where it all began, forced to close schools and ban social gatherings (such as concerts, Testament got canceled, luckily I wasn't planning to but sucks for those who wanted to) for a week.
This is also where all the inevitable comments, due to human nature, begin - it's too much, it's an exageration, what are they hiding etc... it's math. Governments take the decisions they take based on this model. That's why China sealed shut millions of people in their own homes. The value of R0 HAS to be brought below 1. No government in his sane mind would shoot their own economy in the foot AND the balls if it wasn't worth it.
The article mentions also what was discussed here some posts ago - if the number of infected people grows too much, the sanitary system collapses. You can't have hospitals full and people working there falling ill as well. If hospitals are ships, you can't have more people on a ship than the number of cabins, and take the sailors and put them in the cabins as well leaving no one at the helm.
And finally, a quick question: how many Susceptible people there are currently in the world? easy answer. 7 billions. Everyone on the planet. Because there is no vaccine yet. And this is why anti-vaxxers need to be gathered, and taken to an isle in the middle of the ocean and left there to fend for themselves against ferocious beasts.