on a skew to devilsreject's point, i do think that medicine is dragging human biological evolution off at a tangent somewhat.. it helps sustain the lives of people who, for one reason or another, are defective and wouldnt persist to live. natural selection has the potential to cure a lot of illnesses because a condition that kills the carrier runs risk of disappearing itself. in interfering with this, we are going against natural selection's ultimate design plan..
in response to something devilsreject said; dont be too condescending towards medicine with things like "we cant even cure the common cold" - the common cold is a virus, and in incredibly successful one. it is really quite good at infecting a host and we should be thankful that its payload is light. virii mutate, and your body's immune system is not an intelligent, calculating computer that builds antibodies based on logic.. upon infection, your body just throws every antibody it knows how to make, at the infection. any antibodies that are successful are replicated in large amounts. if no antibody is successful, your body produces mutations of them.
it doesnt analyse the structure of a virus and build the perfect antibody first time out..
this is why some people catch the same cold and get affected in different ways or for different times - two or 3 antibodies might work with different effectivenesses for a given strain of virus. if you have the antibody that kills it off very quickly, you dont suffer as much as another person whose antibody is different from yours, and less effective.
for a cold, the biggest problem comes from secondary infections after the virus has finished destroying your cell structure leaving bursted cells as ripe feeding grounds for passing bacteria etc
there is nothing medicine can do to help this, because the virus mutates randomly and there is no way to predict its form - if we could do this, we could also predict the lottery. immunisation usually involves injecting a person with a disabled version of a virus, so the antibodies react to the protein structure and build in some numbers, but the virus (being disabled) cannot replicate (which it would do faster than the antibodies could be tried and assembled). upon real infection, the body has a cache of antibodies that already work, and can more quickly produce additional ones to curb the virus population
its a very politically incorrect thing for me to say, if i were to assert that medicine should not treat some things.. im sure noone would really be prepared to draw the line splitting what should and shouldnt be treated, but in keeping defective organisms alive, we arent doing the future generations any favours..