Viral upper respiratory infection: This is the most common cause of fever, especially in the range of 102°F. It is often self-limiting and can be caused by a variety of viruses such as rhinovirus, coronavirus, or influenza.

Bacterial pharyngitis: Caused by Group A beta-hemolytic streptococcus, this condition can present with fever, sore throat, and swollen lymph nodes.
Influenza: Especially during flu season, influenza can cause high fever, cough, sore throat, and body aches.
Urinary tract infection (UTI): While more common in women, UTIs can cause fever, dysuria, and flank pain in both genders.
Pneumonia: Can present with fever, cough, and shortness of breath, especially in older adults or those with underlying lung disease.

Meningitis: Although less common, meningitis is a life-threatening condition that requires immediate attention. It can present with fever, headache, stiff neck, and altered mental status.
Sepsis: A systemic infection that can lead to organ failure if not promptly treated. It may present with fever, tachycardia, tachypnea, and hypotension.
Appendicitis: Abdominal pain, fever, and vomiting can be symptoms of appendicitis, which requires surgical intervention.
Endocarditis: Especially in patients with a history of heart disease or intravenous drug use, endocarditis can present with fever, new heart murmur, and embolic phenomena.

Lymphoma: Certain types of lymphoma can present with prolonged fever, night sweats, and weight loss.
Tuberculosis: Can cause chronic fever, cough, and weight loss, especially in immunocompromised individuals or those from endemic areas.
Brucellosis: A zoonotic infection that can cause fever, fatigue, and swelling, often related to exposure to infected animals or their products.
Familial Mediterranean fever: A genetic disorder that causes recurrent episodes of fever, often accompanied by abdominal, chest, or joint pain.