Question: Why haven't we found a cure for diseases that have been around for hundreds of years and yet some diseases that have been around a couple of years have been cured even though they are as dangerous as each other?

Mark Burnley answered on 20 Jun 2011:

Curing a disease is about finding the cause of it AND being able to do something about it. A good example of this is infectious disease (germs and viruses): many of these have been cured or are curable because we understand exactly how they infect the body. This is also why we have vaccinations when we are young, because we’ve figured out that giving the immune system a dose of the disease or something similar to it (which is not enough to make you ill) to look at means that it can protect you from it later if you are exposed to it. This has been very very successful, and many diseases have either been wiped out (smallpox) or are so rare that we don’t often see cases of them (polio, tuberculosis). If a new strain of flu is discovered, we can very quickly develop vaccines for it and minimise the risk of death in vulnerable people (the young and old, usually).

The problem is that some diseases cannot be treated by vaccines, or are “chronic diseases” that develop because of poor diet, smoking, industrial exposure, or lack of exercise. There will never be a jab for obesity! Cancer is another disease that is difficult to treat, because it comes in so many forms and is often not detected until it is too late. With these sorts of diseases, we have to rely on “primary prevention” (encouraging people to be healthy) and screening those at high risk (e.g., women with a family history of breast cancer). Some diseases can be detected long before they cause ill health, and in these cases (cervical cancer is a good example) even women who are not at high risk are screened regularly.