Signs and Symptoms

  • Ehrlichiosis typically causes an acute febrile illness.
  • Signs and symptoms vary greatly from person to person.
  • Most people will have a mild or moderate illness, though severe illness and death are possible.
  • Signs and symptoms typically begin within 5–14 days after the bite of an infected tick. However, because tick bites are not painful, many people will not remember a tick bite.
  • Healthcare providers should consider ehrlichiosis or other tickborne infections in the differential diagnosis for patients with a non-specific febrile illness of unknown origin, particularly during spring and summer months when ticks are most active.

Early Illness

The following is a list of signs and symptoms commonly seen in the first few days of illness (days 1–5):

  • Fever, chills, rigors
  • Headache
  • Malaise
  • Myalgia
  • Gastrointestinal symptoms (nausea, vomiting, diarrhea, anorexia)
  • Confusion
  • Rash
    • Rash develops in up to 60% of children, but less than 30% of adults, and typically begins 5 days after symptom onset.
    • The rash usually spares the face, but in some cases may spread to the palms of hands and soles of feet.
    • The rash associated with E. chaffeensis infection may range from maculopapular to petechial in nature and is usually not pruritic (itchy).

Late Illness

If treatment is delayed and ehrlichiosis is allowed to continue, the disease may become severe. Severe illness may involve:

  • Meningitis, meningoencephalitis, and other central nervous system involvement (20% of patients)
  • Acute respiratory distress syndrome
  • Toxic shock-like or septic shock-like syndromes
  • Renal failure
  • Hepatic failure
  • Coagulopathies

Risk factors for severe disease

  • Delayed antibiotic treatment
  • Age: very young and very old
  • Immune-compromising conditions, e.g., advanced HIV, persons receiving chemotherapy or other immune-suppressing medications


Healthcare providers should also look at routine blood tests, such as a complete blood cell count and a chemistry panel when making the diagnosis.

  • General laboratory findings can include absolute leukopenia, thrombocytopenia, and moderately elevated hepatic transaminases.
  • Abnormal laboratory findings can appear in the first week of illness; however, normal laboratory findings do not rule out possible infection.
  • Anemia is reported in about half of patients but generally occurs later in illness.

Clinical Course

Progression of disease varies greatly from person to person and may depend on patient age, co-morbid conditions, immune status, and time of treatment. Patients who are treated early may recover quickly with outpatient treatment with oral antibiotics, while those who experience a more severe course might require intravenous antibiotics, prolonged hospitalization, or intensive care.

Clinical features of E. ewingii and E. muris eauclairensis ehrlichiosis

Symptoms of E. ewingii and E. muris eauclairensis infections are similar to those of E. chaffeensis, although typically less severe. Gastrointestinal symptoms are less common in patients with E. ewingii ehrlichiosis and rash is infrequently described in cases of E. muris eauclairensis. To date, neither E. ewingii nor E. muris eauclairensis infections have been associated with fatalities.

For more in-depth information about signs and symptoms of ehrlichiosis, see: Diagnosis and Management of Tickborne Rickettsial Diseases: Rocky Mountain Spotted Fever and Other Spotted Fever Group Rickettsioses, Ehrlichioses, and Anaplasmosis — United States: A Practical Guide for Health Care and Public Health Professionals (2016) pdf icon[PDF – 48 pages]