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DENGUE FEVER

ARBOVIRAL ILLNESSVIRAL ZOONOSIS- the most rapidly spreading mosquito-borne viral disease in the world-

N. Negrut, MD,Infectious Disease Specialist, Teaching AssistantFaculty of Medicine and Pharmacy, University of Oradea

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DENGUE VIRUSFAM. FLAVIVIRIDAEGENUS FLAVIVIRUSRNA VIRUS4 SEROTYPESTRANSMITTED THRUMOSQUITOES:

Genus Aedes( A. aeqypti,A. albopictus,A. polynesiensis )

The mosquito Aedes aegypti f eeding o ff a human host

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DISTRIBUTIONSUBTROPICAL AND TROPICAL AREAS

50 million dengue infections occur annually

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DENV are efficiently transmitted between mosquitoes and humans.A sylvatic cycle for dengue transmission has been documented in westernAfrica and southeast Asia.

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CL INI CAL FE ATURESINCUBATION: 3 -14 daysCLINICAL MANIFESTATION:

onset abruptthree phases -- febrile , critical and recovery

50-90% asimptomaticNon specific febrile illness

Clasic Dengue fever ( DF)Dengue hemorrhagie fever ( DHF)Dengue shock syndrome ( DSS)

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Febrile phase

FEVER : 41 CBetween 5-7 days+ CH I LL S+ ERYT H EM ATH OS MOTT LING OF T H E SKIN+ FAC I AL FLUS H INGS ADD LEB AC K P ATTERN ( the fever abates for a day and then returns) -more commonly in childrenrisk for development of DHF or DSS at time of defervescence

H EAD ACH E , RETROORBIT AL P A INN AUSE A, VOMITINGSORE T H RO AT , INJE CTED P HA RYNS , CONJUN CTIV AL INJE CTIONR AS H:

m aculopapular/ m acular confluent rash face , thorax , and flexor surfaces , w ith islands of skin sparingtypically begins on day 3 and persists 2-3 days

MYAL GI AS , ART H R AL GI ASH EMORR HA GI C MANIFEST ATION : petechiae and mucosal membrane bleedingH EP ATITIS

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Critical phasewhen the temperature drops, on days 37 of illness and lasts 2448 hours

Warning signs Dengue with warning signs1. Abdominal pain or tenderness2. Persistent vomiting3. Clinical fluid accumulation4. Mucosal bleed5. Lethargy, restlessness6. Liver enlargement >2 cm7. haematocrit8. T

Can appears:- Pleural effusion- Ascites- Severe bleeding

- Severe hepatitis- Encephalitis- MyocarditisFuture evolution of dengue with warning signs:

recover with early intravenous rehydrationor severe dengue

Sequential infection or pre-existing antidengue antibodies increases therisk of DHF through antibody-dependent enhancement.

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Recovery phaseafter 24-48 hours

well-being improves,appetite returns,

gastrointestinal symptoms abate,haemodynamic status stabilizes,diuresis ensues.

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The course of dengue infection

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Types of rash in dengue

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DFfeversevere headacheretro-orbital pain

severe joint and muscle painnausea and vomitingrash

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DHFis characterised by four criteria:

acute onset of high feverhaemorrhagic manifestations :

positive tourniquet test,skin haemorrhages,mucosal and gastrointestinal tract bleeding

thrombocytopeniaplasma leakage :

rise or drop in haematocrit,pleural effusions or ascites ,hypoproteinaemia.

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Tourniquet test

( Rumpel-Leede Capillary-Fragility Test or Capillary Fragility Test)

A blood pressure cuff is applied and inflated to a point betweenthe systolic and diastolic blood pressures for 5 minutes.The test is positive > 10 petechiae per square inch.

A positive tourniquet test on the left side of the image.

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DF-DHF-DSS

C riteria for severe evolution of DF :patient fro m an area of dengue risk + fever 27 days + one of the follo w ing :

plasma leakage : high or progressively rising haematocrit; pleural effusions or ascites; circulatory compromise or shock.

significant bleeding.altered level of consciousness.severe gastrointestinal involvement.severe organ impairment ( acute liver failure, acute renal failure,

encephalopathy or encephalitis, or other unusual manifestations,cardiomyopathy) or other unusual manifestations.

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WH O grading of severity of D H F

Grade Ifever + non-specific constitutional symptoms;haemorrhagic manifestation: positive tourniquet test+/- easybruising.

Grade IIspontaneous bleedingmanifestations of Grade I, usually in the form of skin and otherhaemorrhages

Grade III = DSScirculatory failure ( tachycardia, weak pulse and narrowing of pulse pressure or hypotension, cold, clammy skin,restlessness)

Grade IV = DSSprofound shock ( undetectable blood pressure or pulse).

DF+ thro m bocytopenia + hae m oconcentration= D H F grades I / IID H F grades III / IV = DSS.

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Laboratory S tudies

Complete blood cell countWBC , LymHematocrit level rise of greater than 20% = hemoconcentration

should be monitored at 24 hours for early recognition of DHF3-4 hours in severe cases of DHF or DSS.

T

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Tests for confir m ation :

detection of the virus in cell culture in the first 5 days( serum, plasma,circulating blood cells and other tissues)

detection of viral RNA ( nucleic acid amplification tests - NAAT ) in the first 5days

detection of viral antigens ( ELISA/rapid test) in the first 5 days

antibodies Anti-dengue IgM and Ig G ( A four-fold or greater increase inantibody levels in paired sera ( at 10 days) indicates an acute or recent flavivirusinfection)- after 5 th day of infection.

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D ifferential D iagnoses

Meningococcal infectionsHepatitisInfluenzaRocky Mountain Spotted FeverLeptospirosisSepsisMalariaTyphusMeningitisYellow FeverChikungunya virus infections

Mayaro feverRoss River feverSindbis virus infectionsViral Hemorrhagic FeversSevere acute respiratory syndrome ( SARS)

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Treat m ent self limited diseaseBed rest, fruit juice and other fluids containingelectrolytes and sugar.

NO : IMAcetylsalicylic acid ( aspirin) Reyes SyndromeN on - steroidal anti - infla mm atory agents (NS A ID s) Gastritis or bleeding.

Oral rehydration solution ( ORS)IV fluid: Ringer lactate solution, SodiumChloridePlasma expander ( Dextran 40, Albumin 5%)Blood transfusion, fresh frozen plasma

Antipiretics: ParacetamolSupportive treatmentTreatment of the complication.

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P reventionReduce humanvector contact:

installing mosquito screening on windows,doors and other entry points;

using mosquito nets while sleeping duringdaytime;avoid travel to areas where dengue is endemic;wear protective clothing;eliminate the mosquitoes.

Improvement of water supply andwater-storage systems.No vaccine is currently available.

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