With lyme, IgM persists longer than 'other' infections.
In most infections, the IgM seroconverts to IgG within a few days...to weeks.
But for Lyme - it remains IgM for months to years.
Well-known LLMD Dr. Jemsek wrote this:
"In virtually all infections, the IgM class of antibody (immunoglobulin) appears first and therefore represents a marker for an early infection. In most immune models, the IgM antibody gives way to the well-known IgG antibody class, usually regarded as the major enduring antibody response in chronic infectious diseases or other immune models. In almost all infection models, after just a few weeks, the IgM antibody level wanes to the point of being non-detectable and does not recur. However, a confounding fact in Bb infections is that the IgM antibody may persist for years, a very unusual situation in most disease states. Logically, one would have to conclude that this reflects an ongoing reactivation or persisting and continually renewing infectious state of Bb infection. "
jemsekspecialty.com/laboratory-testing-for-lyme-disease/Note - Dr. Jemsek is also an Infectious Disease Dr. now treating lyme.