Figure. Histologic slides of autopsy tissue from patients who acquired Rocky Mountain spotted fever in northern Mexico and died at hospitals in the United States, 2013–2016. A) Immunohistochemical stain of Rickettsia rickettsii antigens (red) in inflamed blood vessel adjacent to eccrine gland in a skin biopsy specimen from case-patient 1. Immunoalkaline phosphatase with naphthol-fast red and hematoxylin counterstain; original magnification ×50. B) Diffuse pulmonary capillaritis in case-patient 4. Hematoxylin and eosin stain; original magnification ×50. C) Vasculitis involving a small blood vessel in a peripheral nerve of case-patient 4. Hematoxylin and eosin stain; original magnification ×100.