• 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 (DEN-1, DEN-2, DEN-3, DEN-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

 Pathophysiology 

• It is transmitted to humans through the bites of infected Aedes mosquitoes
  • Primarily transmitted by female Aedes aegypti, a tropical & 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 & is associated w/ 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 & progressive decrease in total white blood cell (WBC) count
  • Progression to critical phase should be recognized promptly by monitoring for warning signs & other clinical parameters

Critical phase

• Occurs on day 3-7 of illness & usually lasts for 1-2 days
• Patient’s temperature lowers to ≤37.5-38^oC & may have increase in capillary permeability concurrent w/ 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 & the volume of fluid therapy
• Other patient may proceed w/ this phase even w/o 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 w/ respiratory distress due to massive pleural effusion & ascites if excessive intravenous (IV) fluids were given