What is the latest classification of dengue fever?

Latest Classification of Dengue Fever

The World Health Organization (WHO) revised dengue classification system from 2009 has replaced the traditional classification with three categories: Dengue without Warning Signs, Dengue with Warning Signs, and Severe Dengue, which demonstrates higher sensitivity (92.1%) for identifying severe cases requiring advanced care compared to the traditional classification (39.0%). 1

Traditional vs. Revised WHO Classification

Traditional WHO Classification (pre-2009)

• Categorized dengue into Dengue Fever (DF), Dengue Hemorrhagic Fever (DHF grades I-IV), and Dengue Shock Syndrome (DSS) 2
• DHF was defined as an acute febrile illness with minor or major bleeding phenomena, thrombocytopenia (≤100,000/mm³), and evidence of plasma leakage documented by hemoconcentration (hematocrit increased by ≥20%) 2
• DSS included all criteria for DHF plus hypotension or narrow pulse pressure (≤20 mm Hg) 2

Revised WHO Classification (2009)

• Categorizes dengue into three groups based on clinical severity 3, 1:
  1. Dengue without Warning Signs: Fever with two of the following: nausea/vomiting, rash, aches/pains, leukopenia, positive tourniquet test 1, 4
  2. Dengue with Warning Signs: Dengue plus any of: abdominal pain/tenderness, persistent vomiting, clinical fluid accumulation, mucosal bleeding, lethargy/restlessness, liver enlargement, increasing hematocrit with decreasing platelets 5, 1
  3. Severe Dengue: Dengue with severe plasma leakage, severe bleeding, or organ failure 6, 1

Clinical Utility of the Revised Classification

• The revised classification demonstrates higher sensitivity (92.1%) for identifying severe cases requiring intensive care compared to the traditional classification (39.0%) 1
• It better captures the full spectrum of dengue disease manifestations, including organ impairment that wasn't adequately addressed in the traditional system 1, 4
• Warning signs help identify patients at risk for progression to severe disease, enabling earlier intervention 5, 4

Diagnostic Considerations

• Laboratory confirmation remains important through PCR (most effective in first few days), NS1 antigen detection (days 1-10), or IgM antibody testing (after first week) 5
• Daily monitoring of complete blood count is essential to track platelet counts and hematocrit levels, which helps detect early signs of progression to severe disease 7, 6

Limitations and Proposed Modifications

• Some studies suggest adding decompensation of chronic diseases and thrombocytopenia-related bleeding to the severe dengue category to improve sensitivity from 72% to 98% for identifying patients needing advanced healthcare 8
• The revised classification creates approximately twice the workload for healthcare personnel compared to the traditional system 3
• Definitions of warning signs and severe dengue vary considerably between studies, highlighting the need for standardized definitions 9

Clinical Application

• Presence of any warning sign warrants close monitoring and consideration for hospitalization 6, 5
• Warning signs typically appear around day 3-7 of illness, coinciding with defervescence (fever reduction) 5
• The critical clinical stage for determining progression to severe dengue is the transition from fever to defervescence, when plasma leakage can occur 4

Risk Factors for Severe Disease

• Secondary dengue infection (previous exposure to a different dengue serotype) is strongly associated with severe disease 4
• Higher early viral load correlates with progression to severe disease 4
• DENV-2 serotype was significantly associated with DHF/DSS in the traditional classification, though this association was not observed with the revised classification 1

The revised WHO classification system provides a more practical approach to patient management, with improved sensitivity for identifying severe cases requiring advanced care, though standardization of definitions remains an ongoing challenge.