Rocky Mountain spotted fever

Rocky Mountain spotted fever
Other names	Blue disease,[1] Brazilian spotted fever, Tobia fever, new world spotted fever, tick-borne typhus fever, São Paulo fever[2]
Petechial rash on the arm caused by Rocky Mountain spotted fever
Specialty	Infectious disease
Symptoms	Early: Fever, headache[3] Later: Rash[3]
Complications	Hearing loss, loss of limbs[3]
Usual onset	2 to 14 days after infection[2]
Duration	2 weeks[2]
Causes	Rickettsia rickettsii spread by ticks[4]
Diagnostic method	Based on symptoms[5]
Differential diagnosis	Zika fever, dengue, chikungunya, Rickettsia parkeri rickettsiosis, Pacific Coast tick fever, rickettsialpox[6][7]
Treatment	Doxycycline[8]
Prognosis	0.5% risk of death[6]
Frequency	< 5,000 cases per year (USA)[6]

Rocky Mountain spotted fever (RMSF) is a bacterial disease spread by ticks.^[9] It typically begins with a fever and headache, which is followed a few days later with the development of a rash.^[3] The rash is generally made up of small spots of bleeding and starts on the wrists and ankles.^[10] Other symptoms may include muscle pains and vomiting.^[3] Long-term complications following recovery may include hearing loss or loss of part of an arm or leg.^[3]

The disease is caused by Rickettsia rickettsii, a type of bacterium that is primarily spread to humans by American dog ticks, Rocky Mountain wood ticks, and brown dog ticks.^[4] Rarely the disease is spread by blood transfusions.^[4] Diagnosis in the early stages is difficult.^[5] A number of laboratory tests can confirm the diagnosis but treatment should be begun based on symptoms.^[5] It is within a group known as spotted fever rickettsiosis, together with Rickettsia parkeri rickettsiosis, Pacific Coast tick fever, and rickettsialpox.^[6]

Treatment of RMSF is with the antibiotic doxycycline.^[8] It works best when started early and is recommended in all age groups, as well as during pregnancy.^[8] Antibiotics are not recommended for prevention.^[8] Approximately 0.5% of people who are infected die as a result.^[6] Before the discovery of tetracycline in the 1940s, more than 10% of those with RMSF died.^[6]

Fewer than 5,000 cases are reported a year in the United States, most often in June and July.^[6] It has been diagnosed throughout the contiguous United States, Western Canada, and parts of Central and South America.^[10][2] Rocky Mountain spotted fever was first identified in the 1800s in the Rocky Mountains.^[10]