Dengue Fever

DENGUE FEVER

Background Information:
Dengue infection is endemic in tropical and subtropical countries and is highly endemic in this part of the world – Southeast Asia, the so called hot zone.

Epidemiology:
In the last few months (January – April 2014), there has been an average of 200 cases of Dengue per week notified to the Ministry of Environment, Singapore. This represents a higher than usual incidence, consistent with an ongoing epidemic in this part of the world. In 2013, there were just over 22,000 cases of Dengue notified with a total of 8 deaths up to end December 2013. Children tend to have milder symptoms than adults.

Clinical:
Dengue is caused by an Arbovirus called Dengue virus of which there are 4 strains – Type 1,2,3,4. Infection with a particular strain will confer immunity to that strain but does not confer cross protection to the other strains. Therefore it is possible to have Dengue infection 4 times in a lifetime but this is rare because we have one predominant strain in Singapore and a lesser proportion of a second strain here. Infection is caused by a bite from an infected Aedes mosquito, which is the vector for transmission of Dengue. Very rarely, human to human transmission is reported. The incubation period is 3 – 7 days.

Symptoms include:

  • Fever with muscle aches, headaches
  • Reddish rash and sometimes bruising and bleeding into the skin
  • Eyeball pain (eye muscle pain)
  • Vomiting, diarrhoea and swollen hands and feet
  • Bleeding gums,nose bleeding and rarely vomiting blood
There are 3 syndromes in Dengue infection:

  1. Dengue Fever: usually mild with rash and slightly low platelets
  2. Dengue Hemorrhagic Fever with more rash, bleeding and lower platelet count as well as fluid leakage into lungs, extremities and abdominal bloating (capillary leak)
  3. Dengue Shock Syndrome which is the most severe form of Dengue infection resulting in shock, bleeding, very low platelets, multi-organ failure and death.

Your platelet levels are usually in the normal range of between 140 – 440 X 109/L. In Dengue infection, it can drop to a very low level and the patient can start bleeding. Sometimes, they will need a platelet transfusion if there is bleeding. When the platelets have dropped to < 100,000 /ml , daily monitoring is recommended.

Treatment:There is no specific treatment for Dengue. All treatment are supportive and symptomatic eg. treatment of fever, vomiting, diarrhoea, gastritis or platelet transfusion if bleeding or platelet < 20,000 / ml. There is currently no commercially available Dengue vaccine but some candidate vaccines are in development, hopefully in the next 5-10 years.

Points to Note:
Not all Dengue patients need admission to hospital. Most can be managed as outpatient. Some criteria for admission include:

  1. Dehydration and vomiting requiring intravenous infusion
  2. Rapidly dropping platelets or low platelets early in the disease
  3. Bleeding from any site
  4. Patients with multiple co-morbidities
  5. Shortness of breath or hypotension (Low blood pressure)

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