DENGUE FEVER

INTRODUCTION• A debilitating viral disease of the tropics, transmitted by

mosquitoes, and causing sudden fever and acute pains in the joints.

• Also known as “BREAK-BONE FEVER”.

Dengue virus• Genome: RNA virus• Family: Flaviviridae• Genus: Flavivirus• Arbovirus: Viruses transmitted by arthropods.• Serotypes: There are four forms of this virus; DENV-1, DENV-

2, DENV-3 and DENV-4.

vector• Dengue virus is primarily transmitted by Aedes mosquitoes,

particularly A. aegypti.Other vector species include  A. albopictus A. polynesiensis A. scutellaris

Life cycle of mosquito

transmission

symptoms• Fever • Headache• Pain behind eyes• Skin rash• Muscle and joint pain

Positive tourniquet test

To asses fragility of capillary wallsTo identify thrombocytopenia.20 or more petechiae per 1 square inch. 

pathogenesis• Vector bite allows invasion of virus in blood.• Virus enters WBCs and start reproducing.• WBC secrete signalling proteins (cytokines, interferons),

responsible for primary symptoms.• In severe conditions, virus invades body organs (liver & bone

marrow)• Fluid leakage occurs due to capillary permeability.• Low blood pressure and dysfunction of bone marrow leading

to decrease platelet count.• This enhances bleeding and other complications.

Phases of dengue• Febrile Phase • Critical Phase • Recovery Phase

Febrile phaseObservations include:• Fever • Pains• Vomiting• Patachea

Critical phaseCharacterized by;• Accumulation of fluid in chest and abdomen.• Depletion of blood from circulation• Decrease blood supply to vital organsCritical phase is of two types;• Dengue Shock Syndrome (low blood pressure)• Dengue Haemorrhagic Fever (plasma leakage and low platelet

count)

Recovery phaseThis phase involves Reabsorption of fluidFeatures are;• Itching • Altered consciousness (due to fluid overload)• Fatigue

treatment• Vaccine is introduced but not validated world-wide.• Primary method is elimination of habitat by pesticides/BCA.• Supportive treatment include rehydration whether orally or

intravenously. Blood diffusion can be done in severe cases.• Prevent mosquito bite by;i. Wearing clothesii. Mosquito nettingsiii. Mosquito repellent• Medication in analgesics i.e. ACETAMINOPHEN. • Avoid aspirin (analgesic).