Rickettsia
Rickettsia is a group of bacteria transmitted by ticks, fleas, and mites that can cause serious infections.
Rickettsia Mimics Other Illnesses
Rickettsia infections are illnesses caused by tiny bacteria called rickettsia. Rickettsia symptoms can range from mild to severe. In the United States, Rocky Mountain spotted fever is the most common rickettsial infection. Although these infections can also be acquired through fleas, lice or mites, rickettsia is typically transmitted through the bite of an infected tick.
These infections are primarily divided into two main groups: the Spotted Fever Group and the Typhus Group. The Spotted Fever Group includes diseases such as Rocky Mountain spotted fever, Rickettsia parkeri rickettsiosis, and Pacific Coast tick fever —all of which are transmitted by ticks. Symptoms typically include a fever, headache, rash, and sometimes an eschar (a dark scab at the bite site).
In contrast, the Typhus Group includes murine typhus and the extremely rare epidemic typhus, which are spread by fleas or lice. These infections typically present with high fever, headache, and body aches, with the rash occurring less frequently. While rickettsial symptoms are generally similar within each group, they differ between the two.
Rickettsia infections cause a range of symptoms that are nonspecific and mimic other illnesses. The infection may be mistaken for the flu, viral infections, and other tick-borne diseases. This makes diagnosing rickettsia challenging. Symptoms can range from mild to life-threatening if left untreated.
Rickettsia infections are on the rise in the US
Rickettsia: How It’s Diagnosed and Treated
Rickettsial infections can be difficult to diagnose early because symptoms resemble many other illnesses. The infection is diagnosed based on a patient’s history of exposure to ticks, mites or lice, and the presence of symptoms, such as fever, headache, muscle aches, and possibly, a rash.
Several laboratory tests include: antibody tests (often only positive after the first week of illness); PCR (polymerase chain reaction), which can detect Rickettsia DNA in blood or tissue samples; and blood tests that may show low platelet count, elevated liver enzymes, or low sodium.
Because some rickettsial infections (such as Rocky Mountain spotted fever) can get worse quickly, doctors often start treatment right away — usually with antibiotics — even before lab tests confirm the infection.
Typically, symptoms begin within 2 - 14 days after infection and include:
High fever
Severe headaches
Muscle aches
Fatigue
Gastrointestinal issues (nausea, vomiting, abdominal pain)
Rash — which can be maculopapular (small, raised bumps) or petechial (small red or purple dots)
In severe cases, additional symptoms can appear, such as:
Confusion or altered mental state
Breathing difficulties
Organ dysfunction (liver, kidneys, or heart)
Note: The information presented on this page has been reviewed and approved by a member of our Medical Leadership Board.
Rickettsia infections have been reported in every state in the U.S., except Alaska and Hawaii (where cases may occur but aren’t officially tracked.)
The majority of cases are reported in the Southeastern and South-Central states, including: North Carolina, Oklahoma, Arkansas, Tennessee and Missouri. Rocky Mountain spotted fever (the most common rickettsia infection) is widespread in those regions.
In the United States, rickettsia infections are primarily transmitted by the:
American dog tick (Dermacentor variabilis)
Rocky Mountain wood tick (Dermacentor andersoni)
Brown dog tick (Rhipicephalus sanguineus)
Lone star tick (Amblyomma americanum)
Gulf Coast tick (Amblyomma maculatum)
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