Figure 1.

Sentinel surveillance pyramid showing incomplete capture of Q fever and spotted fever group rickettsioses (SFGR) cases in a surveillance catchment. The adjustment multipliers used to correct for case underascertainment are shown (left side) along with explanations for each (right side). Indirect immunofluorescence assay (IFA) performance multipliers are derived from the literature. Paired sera, enrollment, and time multipliers are derived from study documentation. The hospital multiplier is derived from responses to the healthcare utilization survey. This figure has been expanded and modified from those of Crump et al.⁶³ and Andrews et al.¹⁶