Chikungunya: This diagnosis is often considered due to similar clinical presentations, including fever, joint pain, and rash, and because both diseases are transmitted by the same vectors (Aedes mosquitoes).

Zika Virus: Presents with similar symptoms such as fever, rash, and conjunctivitis, and is also transmitted by Aedes mosquitoes.
Malaria: Although the symptoms can be different, malaria can present with fever and is a significant consideration in endemic areas.
Influenza: Can mimic the early stages of dengue fever with symptoms like high fever and body aches.
Typhoid Fever: Presents with prolonged fever, headache, and abdominal pain, which can be confused with the severe form of dengue fever.

Yellow Fever: Although less common, it's critical to rule out due to its high mortality rate if untreated. Symptoms include fever, chills, loss of appetite, nausea, muscle pains particularly in the back, and headaches.
Meningitis or Encephalitis: In cases where neurological symptoms are present, these diagnoses must be considered due to their potential for severe outcomes.
Septicemia: Bacterial infections that can lead to sepsis may present with fever and shock, similar to the severe forms of dengue hemorrhagic fever.

Leptospirosis: A bacterial infection that can cause a wide range of symptoms, including fever, headache, and muscle aches, similar to dengue fever.
Rickettsial Diseases: Such as scrub typhus or spotted fever, which can present with fever, headache, and rash.
Hantavirus: Can cause hemorrhagic fever with renal syndrome or hantavirus pulmonary syndrome, both of which have severe outcomes and must be considered in endemic areas.
O'nyong-nyong Fever: A viral disease transmitted by mosquitoes, causing fever, joint pain, and rash, similar to dengue fever, but less common and mostly confined to Africa.