Case Presentation: A 43-year-old male with no past medical history presented to the emergency room (ER) with fever, headache and generalized body pains for 3 days. He recently returned to the USA 5 days ago after a three week trip to Northern India to visit his extended family. His vitals signs and physical exam was unremarkable on presentation except for a temperature of 102.3 F. His initial lab work which includes complete blood picture (CBC), comprehensive metabolic profile (CMP), urinalysis(UA) showed mild elevations of aspartate transaminase(AST) up to 65. Imaging included chest x-ray, ultrasound abdomen, and CT scan head and was unremarkable.Lumbar puncture was done which was unrevealing. Because of a fever in a returned traveler, a blood smear was checked for malarial parasites and its negative. Initial testing for dengue titers came back negative. We didn’t start the patient on antibiotics and placed under observation.In the next three days, AST and ALT trended up to 830 and 570 respectively. White blood cell (WBC) count and platelet count dropped to 3.0 and 36 respectively during the same period. Blood tests for hepatitis A, B, C, EBV, CMV, HSV returned negative. His symptoms initially worsened and later got better. He was treated with supportive intravenous fluids during this period. We repeated dengue titers on day 6 of his hospitalization which returned positive. By this time, his AST, ALT, WBC and platelet counts were trending towards normalization. The patient was diagnosed with dengue fever and discharged home. Two weeks post-discharge all his labs were unremarkable.

Discussion: Dengue is a febrile illness caused by infection with one of four closely related but serologically distinct dengue viruses transmitted by bites of Aedes aegypti or Aedes albopictus mosquitoes. Symptoms typically develop between 4 and 7 days after the bite of an infected mosquito. The infection consists of three phases: a febrile phase, a critical phase, and a recovery phase. Clinical manifestations range from self-limited dengue fever to dengue hemorrhagic fever with shock syndrome with a significant mortality rate. Diagnosis is based mainly on clinical grounds in patients exposed to dengue by residence in or travel to a dengue-endemic country or region. IgM antibodies against dengue virus are detectable starting 4-5 days after onset of symptoms and are reliably detectable for approximately 12 weeks. This explains the initial negative titers in our patient. If IgM is negative and the serum was obtained within the first six days after onset of illness, testing the sample for dengue viral nonstructural protein 1 (NS1) antigen by enzyme-linked immunosorbent assay (ELISA) is recommended. Management is supportive, which largely consists of maintaining adequate intravascular volume.

Conclusions: In conclusion, dengue fever is a common tropical infection. This clinical vignette emphasizes the importance of considering dengue fever as a differential diagnosis of fever in a returned traveler, especially to endemic areas. Diagnosis is usually made on clinical grounds. Basic labs and serology, when used in the appropriate context, increases the likelihood of confirming the diagnosis and allowing to instill supportive management.