Dengue Literature Review

Dengue Clinical Classification

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Dengue Clinical Classification

Overview

Dengue illness is classified for clinical management and epidemiological surveillance purposes. Two WHO systems have been in use: the 1997 WHO classification (dengue fever / dengue haemorrhagic fever / dengue shock syndrome; DF/DHF/DSS) and the 2009 WHO classification (dengue without warning signs / dengue with warning signs / severe dengue). The 2009 system was designed to improve triage and early identification of patients at risk of progression to severe disease, and has largely replaced the 1997 system in clinical practice — though debate continues about which system is better suited to pathogenesis research.

Key Points from Literature

2009 WHO Classification (current)

Three categories:

  1. Dengue without warning signs: Fever + ≥2 of: nausea/vomiting, rash, aches/pains, positive tourniquet test, leukopenia; no warning signs present
  2. Dengue with warning signs: Any dengue + at least one warning sign — abdominal pain or tenderness, persistent vomiting, clinical fluid accumulation (ascites, pleural effusion), mucosal bleed, lethargy/restlessness, liver enlargement >2 cm, rapid decrease in platelet count with rising haematocrit
  3. Severe dengue: Severe plasma leakage (DSS, fluid accumulation with respiratory distress); severe bleeding; severe organ impairment (liver, CNS, kidneys, heart) (see Guzman2016 - Dengue Infection)

Three clinical phases

  1. Febrile phase: Sudden high fever; headache; vomiting; rash; leukopenia; lasts 2–7 days
  2. Critical phase: Coincides with defervescence; plasma leakage, thrombocytopaenia nadir, haemostatic impairment; lasts 24–48 hours; most dengue deaths occur here
  3. Convalescent/reabsorption phase: Reabsorption of leaked plasma; risk of fluid overload if IV fluids not adjusted; bradycardia, rash common; occasional complications (encephalopathy, myocarditis)

2009 vs 1997 WHO system

  • 2009 system has greater discriminatory power for detecting patients at risk of progression and needing hospitalisation than the 1997 system
  • 1997 system: Some argue it was better at identifying plasma leakage (the key pathological process in DHF) and served as a better pathogenesis-research classifier; however, it misclassified approximately 32% of severe cases (classified as DF when they needed clinical intervention)
  • Expert consensus in La Habana, Cuba (2013): decrease in disease lethality documented after introduction of 2009 system
  • Some concerns: warning signs less useful in adults than children; high sensitivity but limited specificity → increased hospital admissions during epidemics (see Guzman2016 - Dengue Infection)

Diagnosis timeline and test selection

Day of illnessBest test
Day 1–5 (febrile)RT-PCR, virus isolation, NS1 antigen ELISA/rapid test
Day 5–6 onwardIgM ELISA (most widely used); IgG seroconversion (paired sera)
Any phasePRNT for definitive serology (reference lab)
  • Presumptive dengue diagnosis: positive IgM in a single sample, OR IgG titer ≥1,280 by HI or ELISA
  • Post-2015 complication: Zika virus (flavivirus) causes IgM cross-reaction with dengue serology; dual DENV/Zika testing now recommended where Zika is circulating

Contradictions & Debates

  • The 1997 system’s DHF/DSS categories were more precisely tied to the pathophysiological mechanism (plasma leakage) and may be more useful for research studies. The 2009 system’s “dengue with warning signs” category is clinically pragmatic but mechanistically broader.
  • Warning sign sensitivity/specificity in adults: several studies found warning signs less predictive in adults than children, potentially requiring age-stratified criteria.

Sources

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