In recent years, as deer populations have risen and humans have increasingly encroached upon their lands, the interaction between the species has become more common. Thus, humans have also had more contact with the deer tick and its frequent companion, the Lyme disease spirochete Borrelia burgdorferi. In fact, according to the Centers for Disease Control, more than 16,000 cases of Lyme disease are reported each year. Initial signs of the infection include a characteristic bulls-eye rash and flu-like symptoms, but may progress into debilitating arthritis and neurological malfunctions if left untreated.