落矶山斑点热是在美国最严重及广泛报告的立克次体疾病，亦在美洲等地有病例。落矶山斑点热在其他国家亦被称为「蜱斑疹伤寒」、「托比亚热」（哥伦比亚）及「圣保罗热」或「斑疹热」（巴西）。这种病是由一种由硬蜱所传播的细菌立氏立克次体所引发。初发的征状包括突然的发热、头痛及肌痛，接着会发起皮疹。这种病症在初期很难诊断，但若没有即时及适当的治疗，是可以致命的。

落矶山斑点热首先于1896年在美国爱达荷州的蛇河谷发现，并因其皮疹的特征而被称为「黑麻疹」。这种可怖及致命的病症影响着这个地区数以百计的人。在1900年代早期，病症的漫延北至华盛顿及蒙大拿州，及南至加利福尼亚州、亚利桑那州及新墨西哥州。

Rocky Mountain spotted fever (RMSF), also known as blue disease, is the most lethal and most frequently reported rickettsial illness in the United States. It has been diagnosed throughout the Americas. Some synonyms for Rocky Mountain spotted fever in other countries include “tick typhus,” “Tobia fever” (Colombia), “São Paulo fever” or “febre maculosa” (Brazil), and “fiebre manchada” (Mexico). It is distinct from the viral tick-borne infection, Colorado tick fever. The disease is caused by Rickettsia rickettsii, a species of bacterium that is spread to humans by Dermacentor ticks. Initial signs and symptoms of the disease include sudden onset of fever, headache, and muscle pain, followed by development of rash. The disease can be difficult to diagnose in the early stages, and without prompt and appropriate treatment it can be fatal.