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B. miyamotoi

What you need to know about Borrelia miyamotoi, a newly described human pathogen

What is Borrelia miyamotoi?

Borrelia miyamotoi are spiral-shaped bacteria that are closely related to bacteria that cause tick-borne relapsing fever (TBRF). They are more distantly related to the bacteria that cause Lyme disease. First identified in 1995 in ticks from Japan, the bacteria have since been detected in two species of North American ticks, the black-legged or “deer” tick (Ixodes scapularis) and the western black-legged tick (Ixodes pacificus). These ticks are already known to transmit several diseases, including Lyme disease, anaplasmosis, and babesiosis.

What type of illness does B. miyamotoi cause?

Human infections with B. miyamotoi were first described in 2011 in a report from Russia. Most of the patients had fever, headache, and muscle aches--symptoms typical of TBRF. Symptoms similar to those of Lyme disease, such as the erythema migrans rash (bull’s-eye rash), arthritis, or facial palsy, were uncommon.

Recently, three cases of human infection with B. miyamotoi were identified in the United States. One patient was an elderly, immunocompromised woman with confusion and an unsteady gait. The bacteria were seen in samples of the patient’s spinal fluid, and she recovered when treated with antibiotics. The two other patients had fever, chills, and muscle aches, similar to the symptoms of the patients in Russia.

How do doctors diagnose B. miyamotoi?

Diagnosis currently relies on the use of tests to detect DNA of the organism, called polymerase chain reaction (PCR) tests. These tests are under development and not widely available. North American strains of B. miyamotoi have not yet been successfully grown in culture, a common method for identifying bacterial diseases. Blood tests based on detection of antibodies require further validation. Blood tests for Lyme disease are unlikely to be helpful in diagnosis of B. miyamotoi infections.

How is B. miyamotoi treated?

Physicians have successfully treated patients infected with B. miyamotoi with a 2-week course of doxycycline.

What more do researchers need to know?

The key signs and symptoms of this infection have not been clearly defined. Most studies have focused on hospitalized patients and may have over-estimated the severity of a typical infection.

It is also unclear how common this infection is in the United States.  Researchers have known about B. miyamotoi infection in U.S. ticks since 2001; however, only 3 well-documented cases of human infection have been reported to date.

What is CDC doing?

CDC is working to better define the public health importance of this infection and is reviewing options for tracking the disease with our partners in state and local health departments. CDC is also developing and evaluating laboratory diagnostic tests to genetically detect the presence of B. miyamotoi in infected individuals and their specific immune responses.

How can I avoid this disease?

The route of transmission of B. miyamotoi to humans has not been firmly established, but likely involves the bite of infected black-legged ticks. People living in areas where blacklegged ticks are common should continue to take precautions against tick bites and see their physician if they experience fever, rash, or malaise after a tick bite or after spending time in tick habitat. For more information, visit:

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