Can Borrelia burgdorferi IgG persist after prior exposure and still not indicate active infection?

Prior Lyme disease can leave a durable serologic footprint. In a 69-year-old man, a positive Borrelia burgdorferi IgG result should therefore be interpreted as evidence of immunologic exposure, not as a stand-alone indicator of current infection.

Persistence and clinical evidence

• Long-term human cohort data show persistent IgG 10–20 years after prior Lyme disease in people without evidence of active illness: 25% after earlier Lyme disease and 62% after prior Lyme arthritis.
• CDC and IDSA/AAN/ACR guidance concur that B. burgdorferi-specific IgG—and sometimes IgM—may remain detectable for years or decades after infection has resolved or been eradicated.
• Accordingly, serology should not be used to assess treatment response, establish cure, or infer treatment failure.

Interpretation of a positive IgG result

• Isolated IgG positivity is compatible with remote or resolved infection, but cannot establish that current symptoms represent active Lyme disease or ongoing viable infection.
• Interpretation requires a compatible clinical syndrome, objective findings, relevant exposure history, and use of validated two-tier serologic testing when testing is clinically indicated.
• In the absence of an appropriate Lyme manifestation, a positive IgG result has limited ability to attribute nonspecific symptoms to active borreliosis.

Ancillary testing and practical implications

• PCR is syndrome- and specimen-dependent: blood and CSF testing have limited sensitivity, whereas synovial-fluid PCR can assist in selected seropositive patients with suspected Lyme arthritis.
• PCR positivity also should not be treated as independent proof of viable ongoing infection, since nucleic-acid detection may persist after treatment.

Bottom line

• Persistent B. burgdorferi IgG after prior exposure is well established and may last decades. A positive result supports prior exposure or infection but, by itself, cannot distinguish active Lyme disease from past resolved infection.