The epidemiology of many infectious diseases is relatively straightforward, having a specific, well-defined, easily identifiable etiologic agent (e.g., a bacterium or virus);
(The epidemiology of many infectious diseases; is; relatively straightforward) (The epidemiology of many infectious diseases; having; a specific, well-defined, easily identifiable etiologic agent)
The epidemiology of many infectious diseases The epidemiology of many infectious diseases
is having
relatively straightforward
a specific, well-defined, easily identifiable etiologic agent