The diseases and viruses

How did aids and cancer develop. They didnt have then back then. these diseases are just new. All these new diseases, are they caused by polution? As more we develope there are new viruses. There has been an increase of viruses. Y?

Well, cancer is not new. Errors in cell reproduction have probably caused cancer as long as there have been cells. However, cancer probably wouldn’t be considered a disease unless it occurred in a multicellular organism, so I suppose I’d date the beginning of cancer back to about the beginnings of multicellular organisms. Hardly a new disease.

AIDS has also probably been around for some time; at least since the 1950s, and I’ve heard speculation about signs of AIDS as early as the 1600s in Africa. Every once in a while the virus seems to jump to human hosts.

That’s not to say that new diseases don’t arise, of course. Since the generation time for disease causing bacteria and viruses is short, their evolution, and hence the development of new diseases and new strains of existing diseases can occur relatively rapidly. (Aren’t there three strains of HIV infecting humans now, while it presumably started as one?)

“Cancer” is a whole bunch of diseases, all of which are characterized by abnormal cell growth. More people are dying of cancer nowadays than in the “good old days” mostly because people are living longer. Because people are no longer dying young of typhus or diptheria, they live long enough for cancers to grow to a fatal size (I know I’m oversimplifying, but the OP seems to need small words.0

AIDS is similar to a disease of monkeys in Africa. It is spread by bodily fluids, all it would take is for a cook to be preparing an infected monkey for a meal and accidently cut his own hand. If the monkey were carring a varient of the disease that could barely survive in a human host, that person would be infected. Diseases jump from animal hosts to human hosts all the time; that is how influenza varieties arise almost yearly from the domestic fowl of the world.

Uh…disease in general (and especially infectious diesase) has been declining sharply in the last century or two. True, we’re discovering more causative agents, but that’s mainly because we’re looking for them and we have better tools with which to do the looking. Smallpox, for instance, is all gone now, but used to kill thousands.

Viruses evolve pretty naturally when you get the right DNA together to create it. Once that happens, it’s survival of the fittest. Different viruses appear as they mutate over time. The ones that spread the most last the longest.