not to be used for advertising or in a defamatory context Swollen knee and rash of a 79 year old man with Lyme disease. This is caused by the spirochete bacterium Borrelia burgdorferi, producing swelling, rash, fever, and nerve and heart problems. The bacterium infects humans and animals, and is spread by ticks. The disease causes flu-like symptoms, arthritis, meningitis, and hallucinations. If diagnosed early it can be successfully treated with antibiotics.