Lyme disease can affect the skin, joints, heart, and the nervous system. More than one in four patients never even develop a lyme disease rash. The researchers noted the outcome should not be evaluated after the initial antibiotic treatment, but rather 6–12 months afterwards. In patients with chronic posttreatment symptoms, persistent positive levels of antibodies did not seem to provide any useful information for further care of the patient. Left untreated, symptoms can become more serious and include joint swelling and arthritis (inflammation of the joints), especially of the knees. The flulike illness usually occurs in the warm weather months when flu (influenza) does not occur. Antibiotics can cure most cases of Lyme disease.