DENGUE FEVER

 

Dengue Fever 🦟 

Dengue fever is caused by Dengue virus (DENV), a mosquito-borne flavivirus.It is single stranded RNA virus of the family Flaviviridae , genus flavivirus . It is the most rapidly spreading mosquito-borne viral disease in the world .

  Transmission:

    The Various seri types of the dengue virus are transmitted to humans through the bites of infected Aedes mosquitoes ,principally Aedes aegypti .

Human are the main amplifying , host of the virus. Dengue virus circulating in the blood of viraemic humans is ingested by female mosquitoes during feeding. 

Dengue infected patients are either asymptomatic or symptomatic. Symptomatic patients have one of three clinical presentations:

Incubation period : 4-5 days 

Clinical presentation:

Prodrome phase may present with malaise and headache 

Acute onset : fever with severe generalised pains ( called broken bone fever ) , retro bulbar , pain associated with eye movement, lacrimation, conjuctival redness, nausea, vomiting, anorexia.

Biphasic fever : ( saddle back fever ) :Initially flushing faint macular rash first 24-48 hours then maculopapular scarlet morbilliform rash from day 3-5 on torso , spreading from extremities to trunk and sparing palms and soles.

Suggested dengue case classification and levels of severity 

    Dengue +\ - warning signs 

Probable dengue 

    Live in / travel to dengue endemic area.

    Fever and 2 of the following criteria :

            * Nausea, vomiting 

            * Rash 

            * Aches and pains 

            * Tourniquet test positive 

            * Leukopenia 

            * warning sign 

Different Diagnosis 

Malaria 

Typhoid

Other viral illness

Laboratory confirmed dengue 

Warning signs : 

The Presence of one or more these signs indicates the need for immediate medical evaluation.

 • Abdominal pain or tenderness 

 • Persistent vomiting 

 • Clinical fluid accumulation 

 • Mucosal bleed 

 • Lethargy , restlessness

 • Laboratory: increase in HCT concurrent with rapid decrease in platelet count 

Criteria for severe dengue

Severe plasma leakage 

         * Shock (DDS)

         * Fluid accumulation with respiratory distress .

Severe bleeding 

Severe bleeding as evaluated by clinician 

Severe organ involvement 

 * liver : AST or ALT >=1000

 * CNS : Impaired consciousness 

 * Heart and other organs

Complications 

 ⁃ Dengue shock syndrome 

 ⁃ Pneumonia 

 ⁃ Iritis

 ⁃ Bone marrow suppression 

 ⁃ Hemorrhage 

 ⁃ Hepatitis 

Diagnosis:

Clinical and laboratory tests 

Laboratory tests:

 ⁃ Blood: CBC : Thrombocytopenia and leucopenia 

 ⁃ ESR: Usually normal 

 ⁃ Liver function tests: Increases liver enzymes 

 ⁃ Serological tests : IgG antibody titers 

 ⁃ Isolation of virus RNA and PCR

Management 

No specific treatment for dengue 

Supportive treatment : fluid and electrolytes management, supply adequate nutrition.

Aspirin is contraindicated due to increased risk of bleeding. 

Prevention :

 ⁃ Use of impregnated nets during sleep .

 ⁃ Use of topical insect repellents 

    _Destroy breeding sites of mosquitoes