Amid the uncertainty, a patient-led lobby (the counterculture, as someone has called it) that includes doctors as well as Lyme sufferers advocates a broader definition of the disease, both for treatment and insurance purposes.

But the medical establishment asserts that too liberal a definition—and what are seen as renegade practitioners—has led to irresponsible and potentially dangerous treatment of unrelated maladies misidentified as Lyme.

It's also unknown how many people have died because of Lyme. A 2011 study found that of the 114 deaths reported over a five-year period listing Lyme as a partial or direct cause, only one was consistent with clinical manifestations described by the International Classification of Diseases.

In December 2013, the Centers for Disease Control and Prevention (CDC)