Statistics of flu vs Coronavirus

[Lumene]

What is the statistical likelihood of someone with Coronavirus symptoms having:

A. Flu
B. Coronavirus

Say someone in London mid-40s gets symptoms recovers and assumes they have had Coronavirus so are likely to be immune. How likely are they to be right (or wrong?)

There is no way to know without testing tbh. Do we know it gives immunity?

Not for sure but strong theory according to CMO