Re: James a question.....

this might be a little off topic but I've heard (in school) that when we invaded the native americans a ton of them got sick from us.. it doesn't make sense to me that now people fly here from china, england, africa, everywhere on planes carrying who knows what, yet there aren't widespread epidemics happening 24/7. of course some people might associate this with vaccines, or maybe the babies are just born immune these days (i don't know if that's possible), but what is the reason we aren't getting sick like the native americans from the widespread contact of humans all around the globe, if it's not vaccines doing?

Actually vaccines have absolutely nothing to do with this.

To understand why let me give a basic explanation of antibodies.  Antibodies are formed in response to foreign particles called antigens, such as viruses, bacteria, etc.  We are taught that antibodies are specific to the antigen, which is not entirely true.  Antibodies can vary from highly specific to non specific with most being somewhere in the middle.  It is these antibodies that are the key.   These semi-specific antibodies can react to other antigens creating an immunity to other pathogens with similar surface proteins.  For example, the typhoid vaccine was shown to produce more antibodies to the HIV virus than the HIV virus itself did.  

In short, as we are exposed to various pathogens our bodies produce antibodies that can cross react to other antigens giving us some protection against these other pathogens if they share some of the same protein markers.

When people came from other countries they brought pathogens that were not similar to anything the natives had been exposed to previously.  This is why they were so decimated by these diseases.  If you follow history a little further you will find that the more the outsiders interacted with the natives the less fatalities the natives had from these diseases.  Think about it this way.  By the 1800s the outsiders trying to steal the land from the natives would not have needed guns to kill the natives and take their land.  They could have simply kept introducing the diseases they brought with them to wipe out the natives if the natives had not already started building up a natural immunity to these diseases.  After all vaccines were not being used by the natives.