ABSTRACT
This chapter discusses the epidemiological methods to study the natural history of an infectious disease are touched upon, as well as the study of prognostic markers and cofactors for disease progression. It deals with the transmission, detection, diagnosis and prevention of infectious diseases than with their natural history and treatment. The basic type of design for studying the natural history of an infectious disease is the cohort study. A cohort of patients that have been diagnosed with the disease are followed over time, and events and outcomes recorded. An important issue in the discussion of natural history of infectious diseases is whether a higher dose at infection leads to a more severe disease. Prognostic factors for the outcome of an infection are usually studied in cohorts as well, where clinical and laboratory findings early in the course of disease are compared with different outcomes.
