Dengue fever

What it is

Dengue fever is a viral infection transmitted by Aedes aegypti or Aedes albopictus mosquitoes. The incubation period is 7 days.

It is one of the undifferentiated fevers with an incubation period under 21 days, with malaria, rickettsiae and ehrlichiosis, typhoid fever, viral hemorrhagic fevers, leptospirosis, brucellosis, acute HIV infection and babesiosis.

The other half of that split is worth holding beside it: the fevers whose incubation period is over 21 days are malaria, brucellosis (2-4 weeks or more), schistosomiasis, tuberculosis, visceral leishmaniasis, amebic liver abscess, hepatitis A, B, E, HIV, filariasis, rabies and African trypanosomiasis. Malaria and brucellosis are listed on both sides of that split.

How it presents

The slide carries only leukopenia under clinical manifestations, with eye pain, headache, rash, muscle pain, bone pain, joint pain and nausea and vomiting on the figure beside it. The note under the same slide gives the full list:

• Headache
• Retro-orbital or ocular pain
• Myalgia and/or bone pain: severe muscle pain is always a feature
• Arthralgia
• Maculopapular rash
• Hemorrhagic manifestations: a positive tourniquet test, petechiae, purpura or ecchymosis, epistaxis, gum bleeding, blood in emesis, urine or stool, or vaginal bleeding
• Leukopenia

Two of those carry more weight than the rest. Severe muscle pain is always a feature, so a patient without it is very unlikely to have dengue. And the hemorrhagic line is all these pages hold about severe dengue: no separate list of severe signs is given on them.