Rheumatoid arthritis is categorized as an autoimmune disease, primarily characterized by swelling and pain in multiple joints, particularly in the wrists or ankles. It also causes morning stiffness, and may be accompanied by fatigue, low fever, muscle soreness, and even weight loss. The onset of the disease is generally gradual for most people, and symptoms can vary significantly from one individual to another. A minority of patients may experience a rapid onset of symptoms, developing joint problems within days or weeks. Therefore, during the acute phase of rheumatoid arthritis, patients may experience a mild or moderate fever. However, it is important to differentiate whether this fever is due to an infection or the activity of the disease itself. This can be determined through regular blood tests, erythrocyte sedimentation rate (ESR), C-reactive protein, and related symptoms.