Rocky Mountain Spotted Fever

What is Rocky Mountain Spotted Fever?

Rocky Mountain spotted fever is a serious infectious disease caused by a bacteria (Rickettsia rickettsii) that is transmitted by the bite of an infected tick. Unless treated early, the disease has a mortality rate of 3 to 5 percent (30 percent before antibiotics became available). 

Even in infected areas, fewer than 2 percent of ticks carry the bacteria. Most cases occur between spring and fall when ticks are most active. 

How do you get Rocky Mountain Spotted Fever?

Rocky Mountain spotted fever is transmitted by several kinds of ticks when they bite humans. Some of the ticks that can transmit this disease are found on dogs (American dog tick) or in woods and forests (Rocky Mountain wood tick).  Other ticks in other geographic areas can also transmit this disease. The tick has to remain attached to its host for about 24 hours before spreading the bacteria.

Susceptibility and Resistance

Generally, all persons are susceptible. However, after having Rocky Mountain spotted fever, people usually will have long lasting immunity.

Incubation Period

The incubation period for Rocky Mountain Spotted Fever is 3-14 days.

What are the Symptoms?

The major symptoms of Rocky Mountain spotted fever are very similar to those of a severe flu and include fever that lasts for 2-3 weeks (if untreated), headaches (sometimes very severe), nerve pain, nausea, vomiting, diarrhoea, and a rash that appears in 3-5 days that is often present on the palms and soles of the feet before spreading across the entire body. Very few people with this disease will develop all of the symptoms.  The combination of symptoms varies greatly from person to person.

Preventative Measures

Prompt removal of any ticks and avoiding tick habitats and tick bites is the most effective prevention measure.


Early recognition and treatment with antibiotics reduces mortality. Use of antibiotics after tick bites as a prevention measure is not effective for preventing this illness.


Where Does It Commonly Occur?

Rocky Mountain spotted fever is found throughout the United States (except Hawaii, Vermont, Maine and Alaska), southern Canada, Mexico, Central America, Argentina, Brazil, and Colombia.