Rocky Mountain spotted fever (RMSF) is a bacterial infection spread by a bite from an infected tick. It causes vomiting, a sudden high fever around 102 or 103°F, headache, abdominal pain, rash, and muscle aches.
RMSF is considered the most serious tick-borne illness in the United States. Though the infection can be treated successfully with antibiotics, it can cause serious damage to internal organs, or even death if it isn’t treated right away. You can reduce your risk by avoiding tick bites or promptly removing a tick that has bitten you.
The symptoms of Rocky Mountain spotted fever typically begin between 2 and 14 days after getting a tick bite. Symptoms come on suddenly and usually include:
- high fever, which may persist for 2 to 3 weeks
- muscle aches
- poor appetite
- abdominal pain
RMSF also causes a rash with small red spots on the wrists, palms, ankles, and soles of the feet. This rash begins 2 to 5 days after the fever and eventually spreads inward towards the torso. After the sixth day of infection, a second rash can develop. It tends to be purple-red, and is a sign that the disease has progressed and become more serious. The goal is to begin treatment before this rash
RMSF can be difficult to diagnose, as the symptoms mimic other illnesses, such as the flu. Although a spotted rash is considered the classic symptom of RMSF, about 10 to 15 percent of people with RMSF don’t develop a rash at all. Only about
RMSF is transmitted, or spread, through the bite of a tick that’s infected with a bacterium known as Rickettsia rickettsii. The bacteria spread through your lymphatic system and multiply in your cells. Though RMSF is caused by bacteria, you can only be infected with the bacteria via a tick bite.
There are many different types of ticks. Types that may be vectors, or carriers, of RMSF include the:
- American dog tick (Dermacentar variablis)
- Rocky Mountain wood tick (Dermacentor andersoni)
- brown dog tick (Rhipicephalus sanguineus)
Ticks are small arachnids that feed on blood. Once a tick has bitten you, it may draw blood slowly over several days. The longer a tick is attached to your skin, the greater the chance of an RMSF infection. Ticks are very small insects — some as small as the head of a pin — so you may never see a tick on your body after it bites you.
RMSF is not contagious and can't be spread from person to person. However, your household dog is also susceptible to RMSF. While you can't get RMSF from your dog, if an infected tick is on your dog's body, the tick can migrate to you while you’re holding your pet.
Treatment for Rocky Mountain spotted fever involves an oral antibiotic known as doxycycline. It’s the preferred drug for treating both children and adults. If you’re pregnant, your doctor may prescribe chloramphenicol instead.
If you don't begin receiving treatment within the first five days, you might require intravenous (IV) antibiotics in the hospital. If your disease is severe or you have complications, you may have to stay in the hospital for a longer period of time to receive fluids and be monitored.
If it isn’t treated right away, RMSF can cause damage to the lining of your blood vessels, tissues, and organs. Complications of RMSF include:
- inflammation of the brain, known as meningitis, leading to seizures and coma
- inflammation of the heart
- inflammation of the lungs
- kidney failure
- gangrene, or dead body tissue, in the fingers and toes
- enlargement of the liver or spleen
- death (if not treated)
People who have a severe case of RMSF may end up with long-term health problems, including:
- neurological deficits
- deafness or hearing loss
- muscle weakness
- partial paralysis of one side of the body
RMSF is rare, but the number of cases per million people, known as incidence, has been increasing over the last 10 years. The current number of cases in the United States is now around six cases per million people per
How common is RMSF?
Around 2,000 cases of RMSF are reported to the
Where is RMSF most commonly found?
Rocky Mountain spotted fever got its name because it was first seen in the Rocky Mountains. However, RMSF is more frequently found in the southeastern part of the United States, as well as parts of:
- Central America
- South America
In the United States,
- North Carolina
What time of year is RMSF most commonly reported?
The infection can occur at any time of the year, but is more common during the warm weather months, when ticks are more active and people tend to spend more time outside.
What is the fatality rate of RMSF?
RMSF can be fatal. However, in the United States overall, less than
You can prevent RMSF by avoiding tick bites or by removing ticks from your body promptly. Take these precautions to prevent a tick bite:
If you do find a tick attached to your body, don't panic. Proper removal is important to decrease the likelihood of infection. Follow these steps to remove the tick:
If you feel ill or develop a rash or a fever after having a tick bite, see your doctor. Rocky Mountain spotted fever and other diseases transmitted by ticks can be dangerous if they’re not treated right away. If possible, take the tick, inside the container or plastic bag, with you to the doctor's office for testing and identification.