Epidemiological study designs appropriate for investigating interactions between HIV infection and tropical diseases

Infections with the human immunodeficiency virus(es) (HIV) are likely to have a profound impact on the health of those in many parts of Africa over the next several decades. If there are adverse interactions between HIV infections and the endemic tropical diseases the overall impact of the HIV epidemic will be worse than that predicted based on observations on the natural history of HIV infections in developed countries. With the exception of tuberculosis, the evidence for such interactions is presently lacking, but this may be largely due to the dearth of informative studies. In this paper we outline the kinds of epidemiological studies required to investigate such interactions and discuss some of the problems associated with the investigations.