Dengue Signs and Symptoms

• Globally, estimated dengue infections climb up to 390 million per year, with 96 million symptomatic individuals, with 70% of the burden coming from Asia
• An 8-fold increase has been reported to the World Health Organization (WHO) in the past 2 decades
• Data on dengue cases decreased in 2020-2021 but inconclusive due to the coronavirus disease 2019 (COVID-19) 
• In Singapore, 35,315 cases were reported in 2020, and >12,000 cases have been reported as of June 2022
• An increase of approximately 300 cases compared to the same period in 2021 has been noted by the National Dengue Control Programme (NDCP) of Cambodia, with >1,200 confirmed cases reported within the first 5 months of 2022
• Reported mortality rates from 2000 to 2015 increased from 960 to 4032, with a decline in the total cases in 2020-2021

• Incubation period
  • Extrinsic (within mosquito vector): 8-10 days
  • Intrinsic (within human host): 3-14 days (average of 4-7 days)
• Transmission to humans is usually through the bite of an infected Aedes mosquito
  • 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
• 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
• 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 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°C 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 patients 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 IV fluids were given