Frequency of endpoint titers by year and county for coyote serum samples that were positive in indirect immunofluorescence antibody assay for spotted fever group rickettsia. Coyote samples were taken from seven Arizona, USA counties in April and May of 2016 and 2017. Titers of 64 and 128 were interpreted as antibody-negative, being below the adjusted cutoff titer of 256. Dashed rows indicate that sera were not collected in the given year–county combination. Titers are expressed as the reciprocal of the highest dilution factor that produced a positive result. Cochise and Graham counties are in the southeast corner of Arizona; the other five counties cover roughly the northern half of the state.