A 20-year-old student has acute headaches, vomiting, and a pink macular rash after returning from South America. What is the likely diagnosis?

The symptoms presented in this case—acute headaches, vomiting, and a pink macular rash—are highly suggestive of dengue fever, particularly considering the travel history to South America, where the disease is endemic.

Dengue fever, caused by the dengue virus transmitted via mosquito bites, is characterized by these clinical signs and often includes a sudden onset of fever, severe headaches, retro-orbital pain, and a maculopapular rash that typically appears 3 to 4 days after the onset of fever. The association between travel to endemic areas and the manifestation of these symptoms supports dengue as the likely diagnosis.

While malarial symptoms can include headaches and vomiting, the rash is not a common feature, making that diagnosis less likely. Typhus, caused by rickettsial infections, may present with similar systemic symptoms but typically includes more pronounced fever with eschar or rash patterns that differ from those seen in dengue. Leptospirosis, on the other hand, often presents with flu-like symptoms, jaundice, and renal involvement, which are not highlighted in this case.

Thus, based on the clinical presentation and epidemiological context, dengue fever fits best as the diagnosis here due to its characteristic symptoms and the patient's travel history