OR FOR OLD MEMBERS TO LEAVE OR WE HAVE TO ACCOUNT FOR THE FACT THAT FOR SOME DISEASES JUST BECAUSE YOU'VE HAD THEM IT DOESN'T MEAN THAT YOU CAN'T HAVE THEM AGAIN AND WE NEED TO ADD IN VACCINATION AND TREATMENT FOR SOME DISEASES AS WELL IF WE REALLY WANT TO KNOW HOW THEY SPREAD THROUGH A POPULATION