Differential Diagnosis for a 60-year-old Woman with 10 Days of Fever

Given the patient's age and the duration of fever, the differential diagnosis can be organized into the following categories:

• Single Most Likely Diagnosis
  • Dengue fever: Although the patient's fever has lasted longer than the typical 7-day course, dengue fever can have a prolonged recovery, especially in older adults. The severity and duration can vary, and it's possible that the patient is experiencing a more severe form or a secondary infection.
• Other Likely Diagnoses
  • Chikungunya: Similar to dengue, chikungunya is a viral illness that can cause prolonged fever and joint pain. It's also transmitted by mosquitoes and can have a longer duration of symptoms, especially in older adults.
  • Zika virus: Another mosquito-borne illness, Zika can cause fever, rash, and conjunctivitis. While it's typically milder than dengue, it can still cause significant morbidity, especially in older adults.
  • Influenza or other respiratory viruses: Given the patient's age, influenza or other respiratory viruses could be a consideration, especially if there are respiratory symptoms present.
• Do Not Miss Diagnoses
  • Malaria: Although less common in some areas, malaria is a critical diagnosis to consider, especially if the patient has traveled to endemic areas. It can cause prolonged fever and has significant morbidity and mortality if not treated promptly.
  • Sepsis: Any older adult with a prolonged fever should be evaluated for sepsis, which can be caused by bacterial, viral, or fungal infections. Sepsis is a medical emergency that requires prompt recognition and treatment.
  • Leptospirosis: This bacterial infection can cause fever, headache, and muscle aches, and can be severe if not treated promptly. It's often associated with exposure to contaminated water.
• Rare Diagnoses
  • Viral hemorrhagic fevers (e.g., Ebola, Lassa fever): While extremely rare, these diagnoses should be considered if the patient has traveled to endemic areas or has other risk factors.
  • Rickettsial diseases (e.g., typhus, spotted fever): These bacterial infections can cause fever, headache, and rash, and are often associated with tick or flea bites.
  • Brucellosis: A bacterial infection that can cause fever, fatigue, and swelling, often associated with exposure to infected animals or their products.

Each of these diagnoses should be considered in the context of the patient's travel history, exposure history, and clinical presentation. A thorough physical examination, laboratory testing, and imaging studies may be necessary to narrow down the differential diagnosis and guide treatment.