>>132810695% of the time you will get the stereotypical bullseye rash, and 100% of the time you will experience flu-like symptoms (joint swelling/aching, fever, headache, chills, swollen lymph nodes). If you get this, you have about a week to seek professional medical treatment, where you will be placed on a fairly simple regimen of antibiotics (it's caused by a bacteria, not a virus, and is 100% treatable).
Chronic lyme is an autoimmune disorder that occurs (rarely) when an active case goes untreated for an extended period of time (somewhere around 3-4 weeks after infection or ~2 weeks after manifestation of the rash). Its symptoms can manifest in a variety of different ways, but the most common is chronic fatigue and chronic joint pain without swelling, similar to rheumatoid arthritis. Unexplained, chronic night fevers is another one but is somewhat more rare. The rate at which acute lyme turns into chronic lyme is unknown, as it has been frequently and routinely misdiagnosed, but is supposedly extremely low (<5%). There is no effective treatment for chronic lyme other than pallative care (treating the symptoms individually, such as steroid injections for joint pain). The exact cause of chronic lyme isn't known and the association with acute lyme is circumstantial.
