Introduction

Dengue is one of the most important arthropod-borne viral diseases in terms of human morbidity and mortality. Widespread in tropical and subtropical regions around the world predominantly in urban and semi urban areas.

Dengue occurs from bite of an infected female Aedes mosquito. Aedes mosquito is most frequently found in or near human habitations.

There is a significant risk for travelers in areas where Dengue is endemic and in areas affected by epidemics of Dengue.

Causative agent: Dengue virus – Flavivirus of which there are four (4) serotypes.

Transmission: Transmitted by the Aedes aegypti mosquito, which bites during day light hours. There is no direct person- to-person transmission.

Incubation period: 3 – 14days, commonly 4-7 days

Sign & Symptoms

Pointers to the clinical diagnosis of Dengue infection;

• High continous fever of 3 days or more
• Headache, backache and retrobital pain
• Abdominal pain, vomiting, loose stools
• Petechial haemorrhage and/or spontaneous bleeding
• Rash – generalized flushing/maculopapular/confluent rash with small islands of normal skin.
• Hepatomegaly
• Fall in platelet count that precedes or occurs simultaneously with a rise in the haematocrit
• Normal WBC or leucopenia with relative lymphocytosis
• Normal ESR (
• Shock

Dengue virus infection may present in four different clinical syndromes:

• Undifferentiated fever
• Dengue fever

An acute febrile illness with sudden onset of fever with two or more of the following manifestations:

Headache, retro orbital pain, myalgia, arthralgia, skin rash, haemorrhagic manifestations and leucopenia.

AND Supportive serology (refer to lab diagnosis) OR

Occurance at the same location and time as other confirmed cases of DF.

It is known as ‘breakbone fever’ because of severe muscular pains. The fever maybe biphasic (i.e two separate episodes or waves of fever) Most patients recover after a few days.

• Dengue haemorrhagic
  An acute onset of fever followed by other symptoms resulting from thrombocytopenia, increased vascular permeability and haemorrhagic manifestations.
• Dengue Shock Syndrome
  Supervenes in a small proportion of cases. Severe hypotension develops, requiring urgent medical treatment to correct hypovolaemia. Without appropriate treatment, 40%-50% of cases are fatal. While with timely therapy, the mortality rate is 1% or less.

Complication

Hepatomegaly, pleural effusion, ascites, bleeding in any forms, unusual neurological presentations include mononeuropathies, polyneuropathies, encephalitis and transverse myelitis.

Encephalopathy occurs occasionally and may result from liver failure or electrolyte imbalances and sometimes shock which may lead to death.

Treatment

Specific treatment ? None

Symptomatic treatment

Advise rest, drink plenty of fluids and take regular painkillers (e.g. Paracetamol or Ibuprofen) to relieve symptoms of fever or aching

• Fluid replacement (Plenty of oral or IV fluids),
• Blood transfusion ( packed red cells) in significant bleeding,
• Platelet transfusion is generally avoided unless there is significant bleeding regardless of the severity of thrombocytopenia or platelet count < 10,000/mm3 with impending or established CNS bleed or continuous bleeding from pre-existing peptic ulcer and Antipyretic for fever.

Prevention & Precautions

No vaccine available

Precautions

• Minimize exposure to bites by modifying activities to avoid exposure to vector bites. Aedes mosquitoe peak biting times are a few hours before dusk and after dawn. Avoid outdoor activity during these periods.
• Avoid mosquito bite by applying mosquito repellent to exposed skin. When using sunscreen or lotions, apply repellants last. Reapply whenever sweat or water has removed it. Active ingredient in a repellent repels but does not kill insects. Repellent that contains DEET (N, N-diethylmetatoluamide) is most reliable and long-lasting type (35% DEET provides protection for 12 hours). DEET formulations as high as 50% are recommended for both adults (including pregnant women) and children >2 months of age. It is toxic when ingested and may cause skin irritation. Permethrin is highly effective both as an insecticide and as a repellent. There is little potential for toxicity from Permethrin-treated clothing.
• Use long sleeved clothes and long pant. Avoid wearing dark colours (attract mosquitoes).
• Close windows or shutters at night when indoors. Use pyrethrum insecticide spray (aerosol insecticides), pyrethroid coils or insecticide impregnated tablets in evening before sleep.
• Avoid strong perfumes, hair sprays or after-shaves (attract mosquitoes)!
• Use air-conditioning or good mosquito net especially treated with Permethrin.

References organisation/ support

International Travel & Health, WHO 2006

Control of Communicable Diseases Manual, 18th Edition by David L. Heymann, MD, Editor, 2004

Clinical Practice Guidelines, Management of Dengue Infection in Adults, Ministry of Health Malaysia and Academy of Medicine of Malaysia.

http://travelhealth.co.uk/