Dengue fever summary

1. Dengue Fever

ƒ Flavivirus – 4 different serotypes ƒ Vector: Aedes aegypti & Aedes albopictus mosquitoes ƒ Incubation period : 3 - 10 days (usually 4 - 6 days).
Infectious period : Within 5 days from onset of the illness.
ƒ Notifiable disease ƒ Pathophysiology:
o Increased capillary permeability o Diffused capillary leakage of plasma (3
rd
space fluid loss)
o Haemoconcentration o ± shock
Symptoms & signs Prodromal
ƒ Malaise & headaches for 2 days
Acute onset
ƒ Fever (2-7 days) ƒ Backache ƒ Arthralgia, myalgia ƒ Generalized pain, abdo pain ƒ Lymphadenopathy ƒ LOA ƒ Bleeding gums
ƒ Scleral injection ƒ Pain on eye movt ƒ Lacrimation ƒ Headache ƒ N/V ƒ Relative bradycardia ƒ depression
Fever
ƒ ‘saddle-back’ fever with break on 4
th
-5
th
day
ƒ or continuous fever ƒ usually lasts 7 days
Rash
ƒ initially transient macular rash ƒ maculopapular scarlet morbilliform rash ƒ spreads centrifugally ƒ sparing of palms & soles
Clinical manifestations 1) Dengue Fever
ƒ Characterized by fever, thrombocytopenia, MP petechial rash ƒ Dz severity not related to plt count. Pl t usu decrease just after fever resolves
around day 5 to 7
ƒ Otherwise similar to other viral fevers ƒ Pruritus over palms usually occur later
2) Dengue Haemorrhagic Shock (DHS)
ƒ Usually due to reinfection by another serotype, or in rare cases, a/w infection
of infants with dengue antibodies from mothers
ƒ Thrombocytopenia (<100,000 / mm
3
)
ƒ Haemoconcentration (Hct ↑ by >20% or Hct >45%) ƒ HypoNa
+
< 5 mEq/L
ƒ ± Haemorrhagic manifestations (pet echia, ecchymosis, epistaxis, gum
bleeding, hemetemesis, melena, retinal h’age)
ƒ hepatic enlargement & tenderness – poor prognostic signs ƒ Pleural effusion, hypoalbuminemia, swollen fingers or pedal edema secondary
to increased capillary permeability
ƒ Encephalopathy with N CSF or neurological disturbances (eg seizures, cranial
nerve signs, coma)
ƒ Acute liver failure: a/w altered mental state, abN neurological signs
(hyperreflexia), brain oedema, severe hemorrhage, pul. Oedema, renal failure
& superimposed infection.
ƒ WHO classification
Grade I
Fever, constitutional symptoms, positive tourniquet test
Grade II
Grade I + spontaneous bleeding
Grade III
Grade II + haemodynamic instability w mental confusion
Grade IV
Grade III + shock
* cases are accompanied with thrombocytopaenia & haemoconcentration
**Grades III & IV denote Dengue Shock Syndrome (DSS)
Presentations
ƒ Persistent fever > 3 days recalcitrant to Rx ƒ Severe backaches, headache, myalgia ƒ Rash: maculopapular or flush; petechial with islands of sparing ƒ Abdominal symptoms: N/V, epigastric pain, diarrhea (may be mistaken for
gastroenteritis or viral gastritis)
Diagnostic Criteria
•
Abrupt onset of high fever, continuous and lasting 2 - 7 days, headache, myalgia
and arthralgia.
•
Haemorrhagic manifestations including any of the following: - Positive tourniquet test
- Petechiae, purpura, ecchymosis
- Epistaxis, gum bleeding
- Haematemesis and/or melaena
•
Enlargement of liver.
•
Thrombocytopenia (100,000/mm
2
or less).
•
Haemoconcentration (haematocrit increased by 20% or more)

2. Dx of DHF: The presence of the first two clinical criteria plus thrombocytopenia and
haemoconcentration
Dx of DSS:
•
All the above criteria, plus
•
Shock as manifested by rapid and weak pulse with narrowing of pulse pressure
(<20 mmHg, regardless of pressure levels) or hypotension with cold, clammy skin
and restlessness.
Investigations FBC
ƒ Haemconcentration ƒ Leucopaenia (leukocytosis & neutrophilia
excludes dengue – consider bacterial
infxns)
ƒ Thrombocytopaenia (<100K / mm
3
)
PT/aPTT

U/E/Cr
ƒ hypoNa
+

LFT
ƒ Abnormal liver enzymes (usu AST>ALT)
Dengue serology
ƒ For IgM, which usually develops on day 5 ƒ 30% will be negative at day 5
PCR
ƒ if rapid dx required (before 5 days)
Management ƒ Monitoring: vital si gns, haemoconcentration, daily platelets counts (when plt <100K,
until upward trend is seen), coagulation profile
ƒ Fluid replacement: N/S or Ringer solution (avoid over-hydration in DHF. Might ppt pul.
oedema)
ƒ Correct electrolytes imbalances ƒ Paracetamol for fever ƒ Anti-histamines for pruritus ƒ No IM injections ƒ Complete rest in bed if platelet <50K due to risk of bleeding from accidental trauma. ƒ Plt transfusion when plt <20K. (Risk of spontaneous bleeding) ƒ Note: thrombocytopenia usually worsens AFTER fever resolves ƒ Notifiable disease Acute Mx of DSS ƒ Monitoring: vital si gns, haemoconcentration, daily platelets counts (until upward trend
is seen), coagulation profile
ƒ Oxygen therapy ƒ Fluid replacement: N/S or Ringer solution
ƒ Correct electrolytes imbalances & metabolic acidosis ƒ Once stabilized, prevent pulmonary oedema by careful IV fluid administration ƒ Avoid salicylates for pain relief due to ri sk of bleeding diathesis and association of
dengue with Reye’s syndrome. Avoid hepatotoxic drugs and long acting sedatives
Disposition
ƒ Grade I responding to oral fluid hydration w no Cx – home ƒ Admit all other PTs for IV fluid therapy (significant dehydration, spontaneous
bleeding, bleeding tendency, sever thrombocytopenia, extremes of age, concomitant illnesses)
ƒ Those with platelet counts between 100-140K can be discharge but should return
for f/u serial FBC until platelet normalizes
Complications ƒ DHF – Haemorrhagic tendencies ƒ DSS – 3
rd
space fluid loss, hemorrhage, myocarditis (rare)
ƒ Abdominal pain – due to pancreatitis, hepatitis or retroperitoneal bleed
pleural effusion
ƒ Lungs – ARDS,