Schema of disease development and assessment of population-level disease parameters for arboviral infections. Among a general population, susceptible (nonimmune) persons who are exposed to the bite of infected/infectious arthropods will go on to develop infection, which may become symptomatic or remain nonsymptomatic. Transmission studies, usually based on serologic testing, provide evidence of past and present infections among the target population, but do not quantify human disease or disability. Symptomatic disease (acute and chronic) and cause-specific fatality may be tallied either actively (by public health outbreak investigations) or passively (by health care systems statistics or case series reports). The generalizability of the rates reported for complications (transition to chronic disease) and for arbovirus-related fatality can vary widely depending on the sampling frame, study design, duration of longitudinal follow-up, and accuracy of diagnostics used.