Based on tick data collected in California since 2000, it was found that they carried a new spirochete bacteria. But for the first case of disease caused by Borrelia miyamotoi in the US, it was only confirmed at the end of 2013 in the Northeast region. Since then, no further confirmed cases have been reported in the western region of the country. The hallmark of this disease is fever that comes and goes, accompanied by fatigue, chills, and aches and pains. In severe cases, this disease can develop into inflammation of the brain and surrounding tissue. However, in most cases, the disease resolves on its own. Infected people tend to show low levels of white blood cells and platelets, elevated liver enzymes, and excess protein in their urine.
The only correct method for identifying Borrelia miyamotoi infection is by looking directly at the sequence of genetic fragments in a person's blood or cerebrospinal fluid. It can only be done in certain laboratories. Thus, fewer and fewer cases have been identified so that researchers have not been able to run further clinical trials. So far, two weeks of the antibiotic doxycycline or amoxicillin appears to work in the majority of cases.
Source
American CDC