• According to the World Health Organization, from 1996-2005, incidence of dengue cases increased from 0.4 million to 1.3 million, and reaching as high as 3.2 million in 2015, with the global incidence rate of symptomatic cases coming predominantly from Asia

• Dengue infection is caused by the Dengue virus, which belongs to the family Flaviviridae
• There are 4 serotypes (DENV-1, DENV-2, DENV-3, DENV-4) 
  • Each serotype provides specific lifetime protective immunity against reinfection of the same serotype, but only temporary (within 2-3 months of the primary infection) and partial protection against the other serotypes
• The fifth serotype, DENV-5, is a new variant that follows the sylvatic cycle (transmission of dengue virus to non-human primates) while the other 4 serotypes are transmitted between humans

 Pathophysiology 

• It is transmitted to humans through the bites of infected Aedes mosquitoes
  • Primarily transmitted by female Aedes aegypti, a tropical and subtropical species
  • Other outbreaks were secondary to A albopictus, A polynesiensis, A scutellaris
  • Humans are the main host of the virus
• After 4-10 days of incubation period, illness begins immediately

Phases of Dengue Infection

Febrile Phase

• Patient suddenly develops high-grade fever that commonly lasts for 2-7 days and is associated with facial flushing, skin redness, generalized arthralgia, myalgia, headache, anorexia, nausea, vomiting
  • May also be accompanied by sore throat, injected pharynx, conjunctival injection, mucosal/gastrointestinal bleeding
  • Likelihood of dengue infection is increased by a positive torniquet test and progressive decrease in total white blood cell (WBC) count
  • Progression to critical phase should be recognized promptly by monitoring for warning signs and other clinical parameters

Critical Phase

• Occurs on days 3-7 of illness and usually lasts for 1-2 days
• Patient’s temperature lowers to ≤37.5-38^oC and may have increase in capillary permeability concurrent with increase in hematocrit level
• Patient may develop pleural effusion, ascites, shock, organ impairment, metabolic acidosis, disseminated intravascular coagulation which may lead to severe hemorrhage
  • Depends on the degree of plasma leakage and the volume of fluid therapy
• Other patient may proceed with this phase even without defervescence
  • Changes in the full blood count may be the only guide to determine the onset of plasma leakage

Recovery Phase

• 2-3 days after critical phase has been successfully surpassed
• Patients may present with respiratory distress due to massive pleural effusion and ascites if excessive intravenous (IV) fluids were given