Actually SARS, etc are a kind of famous flu.
But it doesn't mean nothing happened worldwide for a similar case.
The flu virus is always new and most of them are mutated from the older flu viruses or transmitted from animals (like insect).
Basically, once you get flu and cured, your body has developed anti-body and you will never get sick anymore from the same flu, or from the same flu virus.
If you get another flu, it's because of a new kind of flu virus, mutated or transmitted from the animal.
But thanks goodness, it's not as worse as the case in China.
We just need to take a rest and automatically cured.
This kind of flu epidemic, happened every year, every month, every day, but almost all of them are easily be cured.
In the animal world, like insect, there are millions of kinds of viruses waiting to be transmitted to human.
First of all, yes, SARS is just like other flu, but in some where along the genetic line, some genetic mutation happened so that virus did not just create some sort of digestion in the chest and lung, instead it started destroying lung tissue, causing pneumonia.
The thing is, in the west (I can say for UK, Hong Kong and Australia) government are in the national broadcast as to look for symptom of flu and cold when it was in the season, and hence people can avoid getting sick. That is why this does not generally happened in the west.
That part is what I agree with you. The following is what I disagree with you,
First of all, antibodies does not give you immunization from virus, it helps, generate antibody so you can use it to fight the virus, but generally it will not give you 100% shield so, what you said "once you are cured of one virus, and you are immune to it is wrong" Very simple case, if virus can be cure by people who have survive the virus (ie viral antibodies) then there should be cure for all virus such as HIV, Ebola, Marburg Virus. But the truth is, those are remain incurable.
Secondly, we are able to contain SARS is not because we have cure or there are anything we can do, but rather, if you ask any medical professional, they will say we got lucky becuase the incubation period as well as virology and transmission/reproduction rate is not high, hence a simple quarantine works to contain the virus, however, if SARS infectibility and R0 are anywhere near Ebola level, the SARS outbreak we know would be very different. That is because there are absolutely nothing the medical people can do to defeat SARS, what they did is to treat the sympthom, and let the body heal itself, and if it can't then, well, you die....That is how much have done to "cure" SARS.
What the world afraid of is not just the resurgence of SARS, but a comeback with a mutated strain, which either increase the R0 or contact rate or lower the incubation period or expand the latency of showing any sympthom. If this happen, then we have a real problem here.