Dengue

Question 1

What is the presentation of someone with dengue?

Answer 1

Fever plus

Two or more of the following:

• Nausea, vomiting
• Rash: maculopapular or flush; petechial with islands of sparing
• Headache, backache, myalgia
• Retro-orbital pain
• Tourniquet test positive
• Leucopenia

Question 2

What are the investigations done for dengue?

Answer 2

• FBC: thrombocytopenia, leucopenia, raised haematocrit
• LFTs: mild (x2 ULN) to moderate (x 5 ULN) elevated transaminases (usually AST > ALT).
• Day 1-5: NS1 antigen test (common to all serotypes)
• Serology: Positive dengue IgM on acute serum sample. A high-titre IgG antibody may also be indicative of dengue, particularly secondary infection. IgM antibodies appear on approximately the fifth day of illness and last for two months. A 4-fold rise in titres of a pair of acute and convalescent sera is confirmatory.
• PCR for dengue virus within five days of onset may give a more rapid diagnosis.

Question 3

what are the complications of dengue?

Answer 3

• Dengue haemorrhagic fever, dengue shock syndrome (severe dengue)
• Antibody dependent enhancement (ADE)

Question 4

how is dengue managed?

Answer 4

• Supportive mainly
• Paracetamol for fever (avoid non-steroidal anti-inflammatory drugs –> induces qualitative platelet defect).
• Intravenous fluids for hypotension and dehydration (avoid over-hydration precipitating pulmonary oedema in DHF).
• Daily platelet and haematocrit measurement when platelets drop below 100,000/mm3.
• Complete bed rest for platelet count less than 50,000/mm3.
• There is no evidence that prophylactic platelet transfusion (in the absence of bleeding) is beneficial.

Question 5

What are the warning signs suggestive of severe dengue?

Answer 5

Warning signs suggestive of severe dengue may or may not be present. These are:

• Abdominal pain/tenderness
• Persistent vomiting
• Clinical fluid accumulation
• Mucosal bleeding
• Lethargy, restlessness
• Liver enlargement > 2cm
• Haematocrit increase concurrent with rapid decrease in platelet count

Question 6

What is severe dengue?

Answer 6

Severe plasma leakage

• Shock (dengue shock syndrome)
• -> Hypotension, narrowed pulse pressure (< 20 mm Hg) and impaired organ pefusion plus
• -> Bleeding manifestations (e.g. petechiae, ecchymosis, epistaxis, gum bleeding, haematemesis, melena) plus
• -> Thrombocytopenia (< 100 X 109/L)
• -> Evidence of increased capillary permeability: haematocrit increased by >20% above baseline, pleural effusion, hypoalbuminaemia
• Fluid accumulation with respiratory distress

Severe bleeding

• Intracranial haemorrhage (ICH), mucosal bleed (BGIT, vagina 🡪 menorrhagia, oral mucosa 🡪 gum bleed)
• Due to bleeding, haematocrit (HCT) may fall

Severe organ impairment

• Liver: AST or ALT > 1000 IU
• CNS: impairment of consciousness
• Heart or other organs

Question 7

What is the differential diagnosis for dengue?

Answer 7

• Chikungunya (greater focus on arthralgia)
• Zika virus (greater focus on rash, conjunctivitis and normal FBC)
• Malaria
• Typhoid (diarrhoea is usually present)
• Typhus (patient usually presents in 2nd week, generally mild)
• Acute retroviral/HIV seroconversion should be ruled out

Question 8

What is the incubation period of dengue?

Answer 8

5 – 7 days (range 3 – 14 days)

Question 9

What are the 3 phases of dengue fever?

Answer 9

1. Febrile phase: acute onset of fever.
   - Other symptoms include headache, backache, myalgia, maculopapular rash, retro-orbital pain.
   - There may be minor haemorrhagic manifestations, including petechiae and bruising.
2. Critical phase: occurs around the time of defervescence (around Days 3-7 of infection) and lasts for 24-48 hours.
   - Thrombocytopenia usually worsens
   around this time.
   - Patients should be monitored for warning signs of severe dengue.
   - A small proportion of patients develop a systemic vascular leak syndrome that is characterised by plasma leakage (e.g. pleural effusions, ascites), bleeding, shock and organ dysfunction.
3. Recovery phase: resolution of plasma leak and resorption of extravasated fluids.
   - This phase usually lasts 2-4 days.
   - There is a gradual recovery of platelet count during this phase.
   - Some patients may develop a generalised erythematous rash with small islands of sparing.