Rocky Mountain spotted fever
| Pathogen: Rickettsia rickettsii |
| Tick vectors: Dermacentor variabilis, Dermacentor andersoni, Rhipicephalus sanguineus |
| Geographic distribution: Widespread; most common in south-central and south-Atlantic regions |
| Classic presentation: Fever, headache, rash, weakness, malaise, myalgia, thrombocytopenia, anemia, hyponatremia, increased aminotransferase levels |
| Diagnosis: Serologic antibody testing with a 4-fold increase between acute and convalescent serology with a minimum peak titer ≥ 1:64; polymerase chain reaction assay with low sensitivity; immunohistochemistry and cell culture rarely used |
| Treatment: Doxycycline, typically for 7 days (range 5–10 days) |