Lesson 6: Dengue

#🦟 Dengue Fever: A Comprehensive Guide for Medical Students & Practitioners

By: Parajuli SB, 2026
🌐 www.suryaparajuli.com.np

For: Community Medicine (Kathmandu University)
Level: MBBS 6th Semester
Institution: Birat Medical College Teaching Hospital

#🎯 Learning Objectives

By the end of this session, learners will be able to:

• Understand the basics and epidemiology of dengue

• Describe clinical features, diagnosis, and management

• Explain prevention and control strategies

• Discuss recent updates on dengue vaccines

• Apply knowledge in clinical and community settings

#🧬 Introduction to Dengue

Dengue fever is an acute viral illness caused by the Dengue virus (DENV) and transmitted by infected mosquitoes:

• Primary vectors: Aedes aegypti and Aedes albopictus

• Disease spectrum:

  • Mild febrile illness

  • Dengue Fever (DF)

  • Dengue Hemorrhagic Fever (DHF)

  • Dengue Shock Syndrome (DSS)

#🦠 Causative Agent

• Family: Flaviviridae

• Four serotypes:

  • DENV-1

  • DENV-2

  • DENV-3

  • DENV-4

  • ⚠️ What about DENV-5?

    • A fifth serotype (DENV-5) was reported in 2013 from Malaysia (Sarawak region)

    • It was identified in a sylvatic (forest) cycle, not typical human transmission

⚠️ Key Point:

• Infection with one serotype → lifelong immunity to that type

• Only temporary protection against others → risk of severe dengue

#🌍 Epidemiology

• Endemic in more than 100 countries

• Estimated 390 million infections/year

• High burden in:

  • Southeast Asia

  • Caribbean

  • Central & South America

#📊 Trends

• Increasing incidence due to:

  • Urbanization

  • Climate change

  • Poor sanitation

#🌧️ Seasonality

• Peaks during monsoon season

#🔄 Mode of Transmission

• 🦟 Vector-borne: Bite of infected Aedes mosquito

• 👶 Vertical transmission: Rare (mother to fetus)

#⚙️ Pathogenesis

• Virus enters through mosquito bite

• Replicates in host tissues

#🔬 Important Mechanism:

Antibody-Dependent Enhancement (ADE)
→ Leads to severe dengue

#Severe Disease Features:

• Increased vascular permeability

• Plasma leakage

• Shock

#🩺 Clinical Features

#1. Dengue Fever (DF)

• High-grade fever

• Retro-orbital pain

• Rash

• Leukopenia

#2. Dengue Hemorrhagic Fever (DHF)

• Bleeding manifestations

• Thrombocytopenia

• Increased hematocrit

#3. Dengue Shock Syndrome (DSS)

• Hypovolemic shock

• Organ failure

• Medical emergency ⚠️

#🔍 Diagnosis

#Clinical Suspicion

• Fever + mosquito exposure

• Rash, bleeding signs

#Laboratory Tests

• NS1 Antigen: Early detection (Day 1–7)

• IgM/IgG antibodies:

  • IgM → recent infection

  • IgG → past exposure

• PCR: Gold standard

• CBC findings:

  • Leukopenia

  • Thrombocytopenia

  • ↑ Hematocrit

#💊 Treatment

🚫 No specific antiviral treatment

#Supportive Management:

• Paracetamol for fever (avoid NSAIDs)

• Adequate hydration (oral/IV)

• Blood transfusion if required

#Hospitalization Indicated:

• Severe dengue

• Shock

• Significant bleeding

#🛡️ Prevention and Control

#🦟 Vector Control

• Eliminate stagnant water

• Use insecticides

• Biological control methods

#🧍 Personal Protection

• Mosquito repellents

• Long-sleeved clothing

• Bed nets

#👥 Community Measures

• Awareness campaigns

• Environmental sanitation

#💉 Vaccines

• Dengue vaccines exist but:

  • Limited availability

  • Restricted use in many LMICs

• Ongoing research for safer and more effective vaccines

#🏛️ Public Health Strategies

#Integrated Vector Management (IVM)

• Surveillance

• Vector control

• Community education

#National Programs

• Dengue control initiatives

• Outbreak response systems

#🔑 Key Takeaways

• Dengue is a rapidly increasing global health problem

• Severe disease linked to secondary infection (ADE)

• No specific treatment → early detection is crucial

• Prevention relies heavily on:

  • Vector control

  • Community participation

• Climate change & urbanization are driving spread

#📌 Final Note

Dengue is not just a clinical disease—it is a public health challenge. Effective control requires integration of clinical vigilance, vector management, and community awareness.