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Dengue Fever

Title               

Ñ    Dengue Fever

Definition

Ñ    Disease caused by the dengue virus

Aetiology

Virus

Ñ    RNA virus

Ñ    Genus: Flavivirus

Ñ    Group: Arbovirus

Vector

Ñ    Aedes aegypti

Pathogenesis

Ñ    Virus inoculated by bite of infected mosquito

Ñ    Virus replicates in the reticuloendothelial system (possibly lymphocytes)

Ñ    In secondary infections there is a rapid anamnestic antibody response

Ñ    Antigen and antibody complexes form

Results in:

Ñ    Lymphocytic vasculitis:

T-cell dominance

Ñ    Capillary leak:

Causes complications

Clinical Features

History

Incubation period

Ñ    5-9 days

E&M

Ñ    Fever:

Lasts 2-4 days

Rapid defervescence

Afebrile 1 day

Second fever 2-3 days

IS

Ñ    Itchy maculopapular rash

Begins at the extremities

Spreads to the trunk

Spares face

Ñ    Rash coincides with second phase of fever

GIT

Ñ    Anorexia

Ñ    Nausea

Ñ    Vomiting

CNS

Ñ    Photophobia

Ñ    Pain on movement of the eyes

LMS

Ñ    Muscle pains

Ñ    Joint pains

Social History

Ñ    Residence in or travel to a region where dengue is endemic

Examination

E&M

Ñ    Fever

IS

Ñ    Maculopapular rash

CVS

Ñ    Relative bradycardia

HS

Ñ    Generalised lymphadenopathy

Complications

Dengue Shock Syndrome (DSS)

Ñ    Around 5^th day:

Fever settled

Ñ    Drop in blood pressure, cold clammy, low volume pulse, cyanosis

Dengue Haemorrhagic Fever (DHF)

E&M

Ñ    Occurs at the end of the 1^st phase of fever

IS

Ñ    Petechiae

Ñ    Purpura

Ñ    Ecchymoses

CVS

Ñ    Shock

Ñ    Myocarditis

RS

Ñ    Bronchopneumonia:

Secondary infection

GIT

Ñ    Haematemesis

Ñ    Melaena

Ñ    Bleeding gums

RAG

Ñ    Menorrhagia

HS

Ñ    Septic shock

CNS

Ñ    Restlessness

Ñ    Encephalopathy

Investigations

Fluids

Blood

Haematology

Ñ    Elevated haematocrit (increased packed cell volume) in DSS and DHF

Ñ    Leucopaenia

Ñ    Platelets:

Low

Biochemistry

Ñ    Elevated liver enzymes:

Common

Immunology

Ñ    Dengue Antibody:

 IgM and IgG ELISA

Microbiology

Ñ    PCR also possible

Management

Support

Drugs

Ñ    Intravenous crystalloids and colloids

Biological Agents

Ñ    Platelet infusion

Ñ    Fresh frozen plasma

Symptom Relief

Drugs

Ñ    Paracetamol:

Fever

Prevention

Biological Agents

Ñ    Vector control

Prognosis

Ñ    Mortality 10-30 % :

Dengue haemorrhagic fever

Dengue shock syndrome

 

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