Ten Healthy People

Ten isn't really necessary or the limit, just more than two. Can be any race. Can not be all of the same sex. These people have tested consistently healthy, phsyically and mentally. They have no STDs. Stick them in a confine with adquate everything: air/water/food etc to live. Basically a paradise. No contact with the outside world. They can have sex as much as they want, straight and gay, interchange partners, have orgies, whatever.

How long does it take before they develop a STD? If they do at all? Has there been a study like this?