Infectious Mononucleosis (Mono): Caused by Epstein-Barr virus (EBV), it's common in children and can present with intermittent fevers, fatigue, and lymphadenopathy. The prolonged duration of symptoms fits this diagnosis.

Juvenile Idiopathic Arthritis (JIA): This condition can cause intermittent fevers, joint pain, and swelling. It's a common rheumatologic condition in children.
Tuberculosis (TB): Although less common in some regions, TB can cause chronic or intermittent fevers, especially if it's extrapulmonary. Exposure history and travel are important considerations.
Recurrent Infections: Children with immune deficiencies or anatomical issues (e.g., urinary tract abnormalities) might experience recurrent infections leading to intermittent fevers.

Malignancies (e.g., Leukemia, Lymphoma): These are critical to identify early due to their severe prognosis if left untreated. Symptoms can include intermittent fevers, weight loss, and fatigue.
Endocarditis: Although rare in healthy children, it's a life-threatening condition that can cause intermittent fevers, especially if there's a history of heart disease.
Osteomyelitis or Septic Arthritis: These conditions can present with fever and localized pain, and it's crucial to diagnose them promptly to prevent long-term damage.

Periodic Fever Syndromes (e.g., PFAPA Syndrome): These are rare genetic disorders characterized by recurrent episodes of fever without an obvious cause.
Cystic Fibrosis: While primarily known for respiratory and gastrointestinal symptoms, cystic fibrosis can also cause recurrent fevers due to chronic infections.
Chronic Granulomatous Disease (CGD): A rare immune deficiency that makes it hard for the body to kill certain bacteria and fungi, leading to recurrent infections and fevers.