on 1.2.08 with 0 comments

Group: Group IV ((+)ssRNA)
Family: Flaviviridae
Genus: Flavivirus
Species: Dengue virus

  • Dengue (DF) and dengue hemorrhagic fever (DHF) are caused by one of four closely related, but antigenically distinct, virus serotypes (DEN-1, DEN-2, DEN-3, and DEN-4), of the genus Flavivirus.
  • Infection with one serotype does not protect a person against infection with another.
  • Aedes aegypti, a domestic, day-biting mosquito that prefers to feed on humans, is the most common Aedes species.(Unlike the mosquitoes that cause malaria, dengue mosquitoes bite during the day.)
  • Dengue viruses occur in most tropical areas of the world.
  • Dengue is most common in cities but can be found in rural areas.
  • Incubation Period: averages 4 to 6 days, with a range of 3 to 14 days.

Signs and symptoms

  • High fever, up to 105 degrees Fahrenheit
  • Severe headache
  • Retro-orbital (behind the eye) pain
  • Severe joint and muscle pain
  • Nausea and vomiting
  • Rash

The rash may appear over most of your body 3 to 4 days after the fever begins.

Symptoms of dengue hemorrhagic fever include all of the symptoms of classic dengue plus

  • Marked damage to blood and lymph vessels
  • Bleeding from the nose, gums, or under the skin, causing purplish bruises

Symptoms of dengue shock syndrome--the most severe form of dengue disease--include all of the symptoms of classic dengue and dengue hemorrhagic fever, plus

  • Fluids leaking outside of blood vessels
  • Massive bleeding
  • Shock (very low blood pressure)

This form of the disease usually occurs in children (sometimes adults) experiencing their second dengue infection. It is sometimes fatal, especially in children and young adults.


The diagnosis of dengue is usually made clinically. The classic picture is high fever with no localising source of infection, a petechial rash with thrombocytopenia and relative leukopenia. There exists a WHO definition of dengue haemorrhagic fever that has been in use since 1975; all four criteria must be fulfilled:
  1. Fever
  2. Haemorrhagic tendency (positive tourniquet test, spontaneous bruising, bleeding from mucosa, gingiva, injection sites, etc.; vomiting blood, or bloody diarrhea)
  3. Thrombocytopaenia (<100>
  4. Evidence of plasma leakage (hematocrit more than 20% higher than expected, or drop in haematocrit of 20% or more from baseline following IV fluid, pleural effusion, ascites, hypoproteinaemia)
Dengue shock syndrome is defined as dengue haemorrhagic fever plus:
  1. Weak rapid pulse,
  2. Narrow pulse pressure (less than 20 mm Hg)
  1. Hypotension for age;
  2. Cold, clammy skin and restlessness.
Serology and PCR (polymerase chain reaction) studies are available to confirm the diagnosis of dengue if clinically indicated.

Category: Medicine Notes , Microbiology Notes



Post a Comment