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					ARBOVIRAL DISEASES.

DENGUE SYNDROME
DENGU VIRUS – Group B, FLAVIVIRUS VECTOR – Aedes aegypti Female mosquito

Manifestations of Dengue syndrome
1. 2. 3. 4. Asymptomatic. Classical Dengue fever [ DF]. Dengue Hemorrhagic Fever without shock [ DHF]. Dengue Hemorrhagic Fever with shock [ DSS].

Caused by Dengue virus [ DENV] – serotypes 1, 2, 3, 4 Vector: Aedes aegypti, A. albopictus, A. polinesiensis. Self limiting disease.

The Dengue Syndrome
• • • Most common arboviral disease Most important emerging infectious disease in Tropics and Subtropics. Spreading geographically and increasing in numbers since last 30 years . Pandemic since 1998, 1.2 million cases reported from 56 countries. Globally 100 million infections in a year. Yearly 500,000 cases of DHF & About 12,000 deaths.

•
•

Contd……
• SEAR countries : Hyper-endemic in India, Bangladesh, Myanmar , Thailand, Indonesia, Sri Lanka, Maldives since 1997. • In SEAR countries Leading cause of hospitalization and deaths [ next to ADD & Pneumonia] among children < 15 years. • Mainly in Urban & suburban areas. • 1. 3 billion people live in endemic areas. • 20 -30 million infections in a year. • Yearly 200,000 cases of DHF & • Case fatality rate : 3 . 5 %

Situation in SEAR : 4 categories of countries
Cat-A: Myanmar, Indonesia & Thailand Major public health problem. Leading cause of hospitalization & deaths among children, Principal vector: Aedes aegypti, Role of A. albopictus uncertain. Multiple virus serotypes in circulation. Cat-B: Bangladesh, India, Maldives & Sri lanka. DHF emerging disease. cyclical epidemics more frequent, Expanding geographically within the country. Principal vector: Aedes aegypti, Role of A. albopictus uncertain Multiple virus serotypes in circulation. Cat-C: Bhutan & Nepal – Endemicity uncertain, no reported cases. Cat-D: DPR Korea : Non – endemic.

Reasons for Dengue Expansion
1. Declining vector control measures leading to increase in vector population 2. Increasing population density in urban areas 3. Improper water drainage systems 4. Increasing non-biodegradable containers and poor solid waste disposal 5. Increased international travel & trade

1. Classical Dengue Fever. Epidemiology
Dengue serotypes: DEN-V 1, 2, 3, 4. • All serotypes can cause severe and fatal disease • Each serotype provides specific lifetime immunity, and short-term cross-immunity • Both Endemic & Epidemics. • Reservoir: Both Man & mosquito • All ages & both sexes are affected. • Rainy season

Epidemiology: Agent & Vector
Vector: Aedes aegypti & Aedes albopictus, A. polinesiensis 1. Dengue transmitted by infected female mosquito, daytime feeder

Man

mosquito

man
[I.P. 5 – 6 days ]

[0 -5 days of D.][E.I.P. 8 -10 DAYS]

2. Lives around human habitation (Peridomestic habit) 3. Lays eggs preferentially in artificial containers

Contd….
4. Mosquito transmits virus in Temperature: >26 degree C (Virus multiplication) 5. Humidity: > 60 % (life span of mosquito) 6. Mosquitoes infected for life long 7. Transovarian transmission [ vertical transmission] maintains the virus during inter-epidemic periods. More in A. aegypti.

Stages of Transmission

VIRAEMIC HUMAN 1 (duration 0 – 5 days days)

EXTRINSIC INCUBATION PERIOD – MOSQUITO (8-10 days)

INCUBATION PERIOD – HUMAN 2 (5- 6 days)

Clinical features of Classical Dengue Fever
Self limiting disease (Majority). Low case fatality Fever- Sudden onset, high grade 40 – 41 degree C . BIPHASIC . Fever lasts for 7 days. • Severe headache • Retro-orbital pain • Severe Muscle and joints pain • Nausea/vomiting & Anorexia • Colicky pain abdomen, abdominal tenderness • BIPHASIC Rash in 80 % cases . • Sometimes Hemorrhagic manifestations. • Immunity : Against causative serotype and partial immunity against others.

2. Dengue Haemorrhagic Fever
Vector: A. aegypti • Result of infection with several serotypes 1. Acute onset High Fever & Constitutional symptoms for 2 -7 days + 2. Haemorrhagic manifestations • Positive tourniquet test. • Skin hemorrhages: petechiae, purpura, ecchymoses • Gingival bleeding • Nasal bleeding [ Epistaxis ] • Gastro-intestinal bleeding: Hematemesis, Melaena,

3. Enlargement of liver.

Petechiae

Difference between DF & DHF
2 Major pathophysiologic changes: • Plasma leakage - rising haematocrit value. [ > 20% of normal value] • Abnormal haemostasis – thrombocytopenia [ < 100,000 per cu.mm.] Tourniquet Test: Inflate BP cuff to a point midway between systolic and diastolic pressure for 5 minutes • Positive test: 20 or more petechiae per 1 sq. Inch.

Tourniquet Test

Grading of severity of DHF. Four Grades of DHF GRADE 1 • Fever and constitutional symptoms • Only haemorrhagic manifestation: Positive tourniquet test . GRADE 2 • Grade 1 manifestations • + spontaneous bleeding from skin & other sites

Four Grades of DHF contd…
GRADE 3 Signs of circulatory failure (rapid/weak pulse, narrow pulse pressure [< 20 mm. Hg.], hypotension, cold/clammy skin, restlessness) = impending shock! GRADE 4 Profound shock (undetectable pulse and blood pressure)

DIAGNOSIS: • Endemic area • Fever & clinical signs , symptoms, • Positive tourniquet test. Lab. Investigations: • Thrombocytopenia, [ < 100,000 per cu.mm.] • Hct ↑ (>20% increase from base line value), CONFIRMED DIAGNOSIS: • virus isolation • serology (4-fold increase in paired samples) • ELISA Test.

Clinical Case Definition for DHF (WHO, 1997)
4 NECESSARY CRITERIA: 1. Fever, or recent history of acute fever 2. Hemorrhagic manifestations 3. Low platelet count (≤100,000/cu. mm.) 4. Objective evidence of “capillary leakage” • Elevated hematocrit (20% or more) • Pleural effusion or Ascites

Treatment DHF: Symptomatic & supportive
1. 2. 3. 4. • • • • Fluids Rest Antipyretics (avoid NSAIDS) Monitor Vital signs: blood pressure, pulse rate level of consciousness hematocrit, platelet count,

Fluid Therapy Grade I & II :
Volume replacement for 24 - 48 hours. 1. Aim: To maintain effective circulation during the period of plasma leakage 2. Required fluid volume charted for 2-3 hours at a time for entire 24 – 48 hours. 3. Serial haematocrit determination 4 - 6 hourly. 4. Record vital signs to ensure volume replacement 5. Crystalloids- Ringer’s Lactate, 5% Dextrose NS, 5 % Dextrose ½ NS, 6. Colloids: Dextran 40, Plasma, Heamacceal. 7. Estimation of flow [ To avoid fluid overload] : Drop rate / minute : Litres / 24 hrs x 12.

• Volume replacement therapy. • Maintenance of serum electrolytes & acid – base balance [ acidosis DIC Haemorrhage Shock] • Replacement of plasma loss: Crystalloids 10 -20 ml / kg. wt/ hour. • Profound shock: Use colloidal fluid - Dextran or Plasma 10 20 ml / kg. wt/ hour. • Blood transfusion: Indicated in Persistent shock despite fluid replacement. • Infants & Children : 5 % Dextrose 1/4TH NS, 5 % D. 1/2 NS • Discontinue IV fluids when vital signs are stable & hematocrit reading drops, DIURESIS STARTS. • Dangers of More fluid: Respiratory distress , DEATH due to Hypervolaemia pulmonary oedema Heart failure.

Management of Shock in DSS

Prevention & Control
VECTOR

PATIENT
NO specific TREATMENT

SUSCEPTIBLE POPULATION Community Participation NO vaccine

Prevention and control
1. Isolate patients under mosquito net 2. Personal Protection 3. MOSQUITO CONTROL • ANTI-ADULT: Ultra-low volume fogging • ANTI-LARVAL: i. Larvicides--Temephos ii. Biological. iii. Environmental--Long term strategy

Surveillance
Initiate vector surveillance and disease control measures • Community education to Motivate for Community participation • Alert health personnel to report increase / clustering of cases. • Improve facilities for case management of DHF

Public awareness campaign
• Protect yourself from Aedes mosquito that bites in day time! • Decrease breeding sites! • Drain water from coolers, tanks, drums. • Remove water from coolers when not in use. • All stored water containers should be kept covered all the time • Discard solid waste and objects where water collects e.g. Bottles, tins, tyres etc


				
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