The disease is caused by a bacterium called Borrelia miyamotoi, which is a distant relative of the bacterium that causes Lyme disease.
After initially being discovered in 1995 in Japanese ticks, it went on to emerge in Connecticut in 2001 and later in Russia.
Researchers at Yale University say that one-sixth of nearly 300 Russian patients with suspected tick-borne infections were sick from the new bacterium rather than the one that causes Lyme disease.
While no diagnostic tests for the new disease are readily available, tick bites from Borrelia miyamotoi typically do not create the red “bull's-eye” swelling typically seen in Lyme disease patients.
Illustration: Geoffrey Attardo