In reply to Submit to Gravity: Thats not true.. cancer rates, some of them have been smashed, vaccinations have had a huge effect of rates of many childhood diseases. Polio, TB are now rare.
Clean water, creation of sewers were huge, but modern medicine has almost eliminated many diseases which were once rife in the UK. But i'd not say a small portion for the others.
Even surgery itself, once a major killer. So anything you needed surgery for was a good 50% chance of death.
A good book to read is the biography of cancer...