Printed in U.S.A. Kaposi's Sarcoma (KS), KS-associated Herpesvirus, and the Criteria for Causality in the Age of Molecular Biology

Over the past decade, a new understanding of infec-tious disease epidemiology has emerged, promising answers to a number of previously intractable public health questions. Examples exist for chronic diseases, such as peptic ulcer disease, whose origins are now presumed to have an infectious cause. Much of this change is due to the successful development of mo-lecular biologic techniques that allow researchers to study infectious agents in novel and unexpected ways. The intersection of molecular biology with epidemi-ology makes new demands on epidemiologists, who will be increasingly required to evaluate and under-stand molecular epidemiologic approaches to infec-tious diseases. In this context, simple and rigorous population-based epidemiology becomes even mor