I know sampling all 11million people in Wuhan is impossible, but it isn't required.
It's been some time since statistics class, but let's assume a worst case scenario which requires a confidence interval of 1, and a confidence level of 99%
You only need a **truly random** sample of 16616 people in Wuhan to determine the overall infection rate.
I don't know anyone who has contracted the virus.
I'm asking because in the event of a serious outbreak, all countries don't have sufficient isolation facilities or equipment for their medical staff.
So my understanding is that many doctors and nurses (in the real world) are likely to be continually exposed to low levels of COVID-19 due to the nature of their work. That is what we saw initially in Wuhan.
So suppose a doctor or nurse has previously contracted COVID-19 and fully recovered.
And if they were continually exposed to low levels of virus, could they be expected to remain immune to that particular strain?
If they are continuously exposed to a virus that is actively mutating and continuously generating new antibodies against newer versions of the evolving viruses, it is then possible that they will stay immune for a while longer than the general public. However, the danger is that one of these newer generations of viruses might be one of those super bugs and catch the patient off guard. The patient would end up mounting hyper responses to the virus and becoming serious ill or worse.
Our immune system is a highly energy costly operation. I always like to compare our immune system to a locksmith. Imagine a virus being a lock, our locksmith tries to make as many keys as he can and hopes that one of his keys would open the lock. This is what our immune system is doing. We generate countless immune cells, each of which is coated with a unique kind of antibody. If one antibody locks onto the virus, our body will start mass-produce this type of immune cells. This procedure costs a lot of energy. That’s why we feel so bad when we get the flu. If we are continuously exposed like the doctors in your example, our body will eventually be drained and the virus will crack our defense. So not a good idea to be continuously exposed.
Vaccines also uses the same principle, I.e. low level exposure to kickstart the antibody generation process. However, vaccines typically contain only bits and pieces of the viruses that cannot replicate or proliferate. So our body would be exposed to a low level of only bits of viral particles that do not change over time. In an actual infection situation, the virus in our body are alive and are replicating like crazy. So our body would be constantly under heavy attack. So continuous exposure is a very bad idea.
Having live virus vs. vaccine is like having a live tiger in your house vs. having a tiger tooth as decoration on your shelf. A low level of virus would be like a baby tiger. But it’s going to eventually grow up and eat you...
