Dengue fever

Question 1

Cause and transmission

Answer 1

RNA Flavivirus via vector - Aedes mosquito

Also via contaminated blood transfusion, organ transplant, needlestick, in-utero

Question 2

Spectrum of illness

Answer 2

1) Mild
2) Classic

3) Dengue haemorrhagic fever (DHF), Dengue shock syndrome (DSS)
Severe forms manifest after 2-7 day febrile phase

Question 3

Phases of DHF

Answer 3

1) FEBRILE phase: (2-7 days) Viremia-driven high fevers
2) *CRITICAL (plasma leak) phase: (24-48 hours) Sudden onset of varying degrees of plasma leak into the pleural and abdominal cavities
3) CONVALESCENCE (reabsorption) phase: (2-4 days) Sudden arrest of plasma leak with concomitant reabsorption of extravasated plasma and fluids

Question 4

Describe what can happen in the CRITICAL phase of DHF

Answer 4

BIOCHEMICAL:
-thrombocytopenia, leucopenia

-sudden increase in hematocrit (≥20% increase from baseline), presence of ascites, a new pleural effusion on lateral decubitus chest x-ray, or low serum albumin or protein for age and sex

METABOLIC:
From prolonged shock:
hypocalcemia, hypoglycemia, hyperglycemia, lactic acidosis, and hyponatremia

CLINICAL:
-Abdominal pain or tenderness
Persistent vomiting
Clinical fluid accumulation (i.e., pleural effusion or ascites)
Mucosal bleeding
Lethargy or restlessness
Liver enlargement (≥2cm)
Tachycardia, narrowing pulse pressure

• period of highest risk for developing the severe manifestations of plasma leak and hemorrhage
• vital to watch for evidence of hemorrhage and plasma leak into the pleural and abdominal cavities
• Intracranial bleed
• > intravascular depletion ->cardiovascular compromise -> shock