DENGUE FEVER

DEFINITION

EPIDEMIOLOGY

AETIOLOGY

Caused by 4 distinct but related viruses, DEN- 1/2/3/4- classified under Flaviviridae family

ssRNA viruses, enveloped and spherical (50 nm)Infection by one type confer lifelong immunity

towards that type, but only partial towards other type.

Evidence increase risk for DHF if there is sequential infection

Vector : Aedes aegypti (main), Aedes albopictus & Culex quinquefasciatus

A.aegypti (day-time bitting mosquito)

-must be infective female

-prefer feeds on human (abundant around human.

-breeds in clear water

-bitting activity reduced in low temperature

14ºC(transmission less in winter)

Transmission

Classification

Clinical Manifestation

Dengue Fever- 1◦ Infection with DEN-2 and DEN-4 are thought to be

inapparent, regardless of age- 1◦ infection with DEN-1 & DEN-3 in adult produces

biphasic fever and rash.- Manifestation varies, in infant & young child –asymptomatic to 1-5 days

fever, rhinitis, mild cough, pharyngeal inflammationIn classic dengue fever

- after incubation 2-7 d, rapid & sudden onset of fever

Accompanied by frontal or retro-orbital headacheBack pain (precedes fever,occassionally)Macular rash (transient, generalized,in first 2 days of

fever)Pulse rate is slow ( in proportion to fever)Myalgia ( increase in severity)Nausea & vomiting (on 2-6 D of fever) Generalized Lymphadenopathy , followed by of period of

Defervescence.Generalized mobiliform, maculopapular rash(palm &

soles spare)- disappear in 1-5 D (Biphasic ◦C curve)

At any stage, petechiae,epistaxis & purpuric lesion occur (not common)

After febrile stage, prolonged asthenia, bradycardia & extrasystole note( common in adult)

Dengue Hemorrhagic Fever( DHF).

~Other suggestive signs: hepatomegaly, circulatory disturbance, hematocrite fall after fluid replacement

Clinical Manifestation

Dengue Hemorrhagic Fever (DHF/ DSS) An acute vascular permeability syndrome followed with

abnormal in hemostasis.Progression of illness is characteristics (in children).In mild 1st phase: abrupt onset of fever, malaise,

cough, vomiting, headache & anorexia ( after 2-5 Days of rapid deteroriation & physical collapse)

In 2nd phase: has clammy hand, cold, warm trunk. Flush face & diaphoresis.

Restlessness, irritated, complained of mid-epigastric pain.

Peripheral cyanosis may occur.

Scattered petechiae on forehead, extremities, spontenous ecchymoses, easy bruising and bleeding at site of venupuncture( common findings).

Respiration is rapid & often laboured.The pulse pressure is usually narrow (≤20 mmHg),

systole & diastolic pressure may be low or unobtainable.Liver become tender ( 2-3 fingerbeadth below costal

margin, firm & nontender)Bilateral or unilateral pleural effusion (radiograph)After 2-3 Days of crisis, convalescence is rapid in

children who recovered.Temperature may return to normal during or before

shock.

PATHOGENESIS

On micrscopic exam.maturation arrest of megakaryocytes in BM( D/t vasoactive amines )

Diagnosis

WHO Grading of DHF/DSS

Grade 1 Grade 2 Grade 3 Grade 4

-Fever with constitutional symptoms.-Positive Hess test

-Spontenous bleeding(skin±other bleeds) in addition to manifestation of Grade 1

-Circulatory failure (rapid weak pulse, narrow pulse pressure <20mmHg, but systolic BP still normal.

-Profound shock (hypotension, undetectable BP & HR).

-Grade 3 & 4 is Dengue Shock Syndrome (DSS).-Thrombocytopenia & hemoconcentration differentiate Grade 1 & 2 of DHF from DF.

Investigation

TREATMENT & MANAGEMENT

Dengue Fever: Mostly supportive.Antipyretic drugs or cold sponging (< 40ºC).Fluid & electrolyte are given when necessary.Aspirin is contraindicated ( avoid Reye Synd.)

DHF/DSS: No antiviral given, only supportive measures.Antipyretic to avoid convulsion .Fluid intake is monitored (by mouth)

Observe sign of shock in children.Oral & parenteral fluid therapy for rehydration (to correct

metabolic aacidosis or dehydration).

ShockNeed admission.obtainIV access. & resuscitate.Monitor : vital signs, PCV, ABG, BP hourly until stable,

platelet count 6 hourly, BUSE & urine output.Fluid maintenance- continue with .45%saline 5%

dextrose(1-2 maintenance)

Electrolyte and metabolic disturbance.

-correction of hypoglycemia.Transfusion of blood & blood products.Monitor coagulation profile.O2 supplement.Vitamin K & H2 antagonist.

Prevention & Control

-Education

Prognosis

Only 1/3 of DHF patient develop shock and circulatory failure ( outpatient Tx is enough , bring back when there are alarming signs) .

Early plasma, fluid & electrolyte replacement proved to have favourable outcome( maintain circulation).

In DHF/DSS case, great care taken to reduce invasive procedures while managing shock.

In children,

-in shock with unobtainable BP,

-in shock but delayed admission,

-in shock with GIT bleeding

Has poor prognosis