Four out of five B. miyamotoi sera tested positive on the Hybrid Lyme ELISA, presumably due to the strong homology between the C6 peptide sequence of B. burgdorferi and that of the related B. miyamotoi (20, 21); however, prior or co-infection with B. burgdorferi cannot be ruled out, as three out of the four reactive samples also tested positive by the Lyme IgM immunoblot, which has been reported to be infrequently positive with B. miyamotoi sera (21). Here, CD40LG is linked to coinfection.