Structure & Property

Transmission

Pathogenesis

Clinical findings

Laboratory diagnosis

Treatment

Family: flavivirus

Genome: single-strand, +ve polarity RNA.

Size: 40-50nm

Icosahedral nucleocapsid.

Enveloped virion

Single serotype

Endemic in South America and West Africa.

Two forms:

- urban: disease of humans transmitted by mosquito Aedes aegypti, which breeds in stagnant water.

- jungle: disease of monkeys transmitted by treetop mosquitoes of  haemagogus species.

Most important arbovirus haemorrhagic fever, being the most severe, in which liver involvement and jaundice are prominent features.

No chronic infection.

Lifelong immunity.

Begins with sudden onset of fever, headache, myalgias & photophobia.

After prodrome, symptoms progress to involve the liver, kidneys, and heart.

Prostration and shock accompanied by upper gastrointestinal tract hemorrhage with hematemesis, follows.

Complication: toxic nephrosis with proteinuria.

Diagnosis:

- haemagglutiation-inhibition for rise in antibody titer.

- IgM and IgG ELISA

No antiviral therapy and mortality rate is high.

Yellow fever vaccine:

- contains live attenuated virus of a strain 17D, attenuated by repeated passage in chick embryos.

- administration in one dose by subcutaneous injection.

- provides good, solid immunity for at least 10 years.

- free from side effects.