Syphilis, caused by the bacterial spirochete Treponema pallidum, remains a prominent sexually transmitted infection worldwide.
[doi.org]
This exposure in particular is caused by the spirochete, Treponema pallidum.
[en.wikipedia.org]
Differential diagnosis includes the various causes of a lymphocytic meningitis, including enteroviruses, HSV, HIV, other spirochetes, mycobacteria, fungi, drug reactions,
[std-aid.com]