Structure & Property

Transmission

Pathogenesis

Clinical findings

Laboratory diagnosis

Treatment

Family: flavivirus

Genome: single-strand RNA, +ve polarity.

Size: 40-50nm

Enveloped spherical virion.

4 serotypes: 1, 2, 3 and 4

Envelope glycoprotein contains antigenic determinants:

- group specific

- subgroup specific

- type specific

Aedes aegypti is the main vector.

Man is the main reservoir of dengue virus.

Dengue virus deposited in skin by biting mosquito vector.

Replicates initially at site of infection and in local lymphatic tissue.

Viraemia within a few days.

Virus replicates in mononuclear phagocytes.

Immune enhancement hypothesis:

- non-neutralizing antibodies form complexes with viruses

- internalized into phagocytes where it replicates and spreads.

- antibody-antigen complex activates complement, leading to increased vascular permeability, shock and hemorrhage.

Reinfection with another serotype is more severe as large amounts of cross-reacting antibody to first serotype is produced.

Can be asymptomatic.

Symptomatic:

- dengue fever

- dengue haemorrhagic fever/dengue shock syndrome

Dengue fever:

- abrupt onset with high fever.

- severe headache

- pain behind the eyes

- muscle & joint pains

- rash

Dengue haemorrhagic fever:

- high fever, 2-7 days.

- petechiae, purpura, ecchymosis, epistaxis, gum bleeding.

- enlargement of liver

Dengue shock syndrome:

- onset: acute abdominal pain.

- duration of shock is short: patient may die within 12-24 hours.

Does not cause splenomegaly.

Diagnosis:

- haemagglutiation-inhibition for rise in antibody titer.

- IgM and IgG ELISA

Management:

- prognosis depends on early recognition of shock, based on careful monitoring.

- correction of plasma leakage by volume replacement – infusion of plasma.

- salicylates should be avoided (cause bleeding).

Prevention:

- drain stagnant water.

- mosquito repellant

- insecticide to kill mosquito.