Diseases with Similar Symptoms

Various features of Lyme disease can be mimicked by many other illnesses. Depending on the symptoms, a doctor may be able to perform the evaluations necessary to rule out other conditions.

Ruling Out Other Tick-Borne or Spirochete Infections

Other infections can produce fever, headache, muscle aches, fatigue, and some of the neurologic or cardiac features of early Lyme disease. Some are transmitted by the same tick as Lyme disease.

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Co-Infections Transmitted by the Ixodes Tick. Babesiosis and human granulocytic ehrlichiosis (HGE) are transmitted by the same tick that carries Lyme disease. People are often coinfected with one or more of these infections, which can all cause flu-like symptoms. If these symptoms persist and there is no rash, it is less likely that Lyme disease is present. Still diagnosing a coinfection is difficult.

Other Spirochete Infections. Leptospirosis is a spirochete infection spread through animals or contaminated water that most often affects young people during the summer or fall.

Other Tick-Borne Infections. A number of other tick-borne diseases may resemble Lyme disease, although they are more prevalent in other parts of the country.

• Tick-borne relapsing fever, a flu-like illness that occurs in mountainous areas of the West during the summer, may be under-reported and misdiagnosed as Lyme disease.
• Rocky Mountain spotted fever, which is also transmitted by ticks, is most prevalent in the south central and southeastern parts of the United States, but occurs throughout North and South America. The most characteristic symptom is a spotty rash that appears 5 to 10 days after infection. The disease is caused by ticks that carry the bacterial organism Rickettsia rickettsii, and is considered the most severe tick-borne illness in the United States. Unlike Lyme disease, which is rarely fatal, Rocky Mountain spotted fever causes death in 10% of all cases. Recent outbreaks of Rocky Mountain spotted fever have been linked to increases in wild dog populations.
• A tick-borne infection carried by the Lone-Star tick strongly resembles Lyme disease, including a similar rash. It is not caused by the Lyme spirochete, however, and has been identified in patients who live in the southern United States.