Skip directly to search Skip directly to A to Z list Skip directly to page options Skip directly to site content

Rocky Mountain spotted fever (RMSF) is a tickborne disease caused by the bacterium Rickettsia rickettsii. This organism is a cause of potentially fatal human illness in North and South America, and is transmitted to humans by the bite of infected tick species. In the United States, these include the American dog tick (Dermacentor variabilis), Rocky Mountain wood tick (Dermacentor andersoni), and brown dog tick (Rhipicephalus sanguineus).  Typical symptoms include: fever, headache, abdominal pain, vomiting, and muscle pain. A rash may also develop, but is often absent in the first few days, and in some patients, never develops.  Rocky Mountain spotted fever can be a severe or even fatal illness if not treated in the first few days of symptoms. Doxycycline is the first line treatment for adults and children of all ages, and is most effective if started before the fifth day of symptoms. The initial diagnosis is made based on clinical signs and symptoms, and medical history, and can later be confirmed by using specialized laboratory tests.  RMSF and other tickborne diseases can be prevented.

Related Tick Topics

Avoiding Ticks

Avoid getting infected…On CDC’s Ticks website

Tick Lifecycle and Hosts

How ticks spread disease…On CDC’s Ticks website

Removing a Tick

How to remove a tick…On CDC’s Ticks website

Other Diseases Caused by Ticks

Learn more about other tickborne diseases that can affect your health…On CDC’s Ticks website

New materials for this tick season:

  • Medscape Expert Commentary — Tickborne Rickettsial Diseases: Updated Guidelines for Patient Diagnosis and Management.
  • COCA call—Little Bite, Big Disease: Recognizing and Managing Tickborne Illnesses. Free CE available!
  • MMWR Recommendations and Reports—Diagnosis and Management of Tickborne Rickettsial Diseases: Rocky Mountain Spotted Fever and Other Spotted Fever Group Rickettsioses, Ehrlichioses, and Anaplasmosis — United States. Free CE available!
  • Borrelia miyamotoi – What you need to know about Borrelia miyamotoi