probably the most important arthropod-borne viral disease worldwide, with ~390 million infections occurring per year, of which ~96 million cause signs of disease
Dengue
Vectors of Dengue
- A. aegypti,
- A. albopictus
- mosquitoes typically breed near human habitation, using relatively fresh water from sources such as water jars, vases, discarded containers, coconut husks, and old tires.
- These mosquitoes usually inhabit dwellings and bite during the day.
A. aegypti
- “cause symptomatic infections or asymptomatic seroconversion
- begins after an incubation period averaging 4—7 days
- “break-bone fever”
- After the incubation period, the illness begins abruptly and, in patients with moderate to severe disease, is followed by 3 phases - febrile, critical and recovery
DENGUE
The warning signs mark the beginning of the critical phase
- Abdominal pain or tenderness
- persistent vomiting
- clinical fluid accumulation
- mucosal bleed
- lethargy, restlessness
- liver enlargement >2cm
- Lab: increase in HCT concurrent with rapid decrease in platelet count
- General wellbeing improves
- appetite returns
- gastrointestinal symptoms abate
- haemodynamic status stabilizes
diuresis ensues
Recovery Phase
Heterotypic reinfection may result in classic dengue or, less commonly, in
sever dengue
The induction of vascular permeability and shock depends on multiple factors:
- presence or absence of enhancing and nonneutralizing antibodies,
- age
- Sex
- race
- nutritional status
- sequence of infections (e.g., dengue virus 1 infection followed by dengue virus 2 infection seems to be more dangerous than dengue virus 4 infection followed by
dengue virus 2 infection).
Criteria for Severe dengue
- Severe plasma leakage leading to
- shock
- fluid accumulation w/ respi distress
- shock
- Severe bleeding
- Severe organ involvement
- liver: AST or ALT >=1000
- CNS: Impaired consciousness
- Heart and other organs
Criteria for dengue warning signs
Probable dengue
- Live in/travel to dengue endemic area
- fever and 2 of the ff:
+ nausea, vomiting
+ rash
+ aches and pains
+ tourniquet test positive
+ leucopenia
+ any warning signs
Dengue diagnostics: Virus Detection
Clinical Sample: Acute serum (1-5 days fever) and necropsy tissues
Diagnostic Method:?
- Viral Isolation: cell culture inoculations (>=1 week)
- Nucleic acid detection: RT-PCR (1/2 days)
- Antigen detection: NS1 Ag ELISA (1 day)
Immuno-histochemistry (2-5 days)
Dengue diagnostics: Serological response
Clinical Sample: Paired sera (acute sserum from 1-5 days & 2nd serum 15-21 days after)
Diagnostic Method:?
- IgM or IgG seroconversion: ELISA & HIA (1-2 days)
Neutralization Test (>7 days)Dengue diagnostics: Serological response
Clinical Sample: Serum after day 5 of fever
Diagnostic Method:?
- IgM detection (recent infection): ELISA (1/2 days)
Rapid tests (mins) - IgG detection: IgG ELISA and HIA (1-2 days)
Stepwise approach to the management of dengue
STEP 1- OVERALL ASSESSMENT
- 1 History + symptoms, past med and fam hx
- 2 PE + full physical and mental assessment
- 3 Investigation + including routine lab tests and dengue-specific lab tests
STEP II- DIAGNOSIS, ASSESSMENT OF DISEASE PHASE AND SEVERITY
STEP III MANAGEMENT
III.1 Disease notification
III.2 Management decisions. Depending on the clinical manifestations and other circumstances, patients may
- be sent home (Group A)
- be referred for in-hospital management (Group B)
- required emergency tx and urgent referral (Group C)
These are px who are able to:
- tolerate adequate volumes of oral fluids
- pass urine every 6 hrs
- do not have any of the warning signs particularly when the fever subsides
- have stable hemocrit
Group A
- Co-existing conditions such as pregnancy, infancy, old age, diabetes mellitus
- social cicumstances such as living alone, living far from hospital
- existing warning signs
Group B
- severe plasma leakage with shock and/or fluid accumulation with respiratory distress
- severe bleeding
- severe organ impairement
Group C
Fluid management of compensated shock in adults
Isotonic crystalloid (IV)
IV fluid should be reduced or discontinued if:
- signs of cessation of plasma leakage
- stable BP, pulse anf peripheral perfusion
- hematocrit decreases in the presence of a good pulse vol
- improving urine output
Discharge criteria in px who have dengue
All of the ff conditions must be present:
Clinical
- No fever for 48hrs
- Improvement in clinical status ( general well-being, appetite, haemodynamic status, urine output, no respi distress)
Lab
- increasing trend of platelet count
- stable haematocrit w/o IV fluids
Prognosis of dengue fever
- good
- should avoid use of drugs that supress platelet activity
Prognosis of Dengue hemorrhagic fever
- adversely affected by late dx and delayed or improper tx
- death has occured in 40-50% of px with shock, but with adequate intensive care, deaths should occur in <1% of cases
- many fatalities are caused by overhydration
