Dengue - clinical course

The course of the infection may be asymptomatic, atypical, “classical” or can evolve to a haemorrhagic syndrome with or without shock.

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Classical dengue fever begins fairly suddenly with fever, headache and sometimes lymphadenopathy. There is no splenomegaly. There is marked muscle pain (breakbone fever), especially in the back and in the extraocular eye muscles (pain behind the eyes when looking sideways). The course of the fever is typically in two episodes (biphasic fever). A rash may appear around the 3^rd to 5^th day in a minority of patients. After the fever has disappeared, recovery may be long and difficult.

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Complicated dengue is rare. Sometimes dengue infection is accompanied by haemorrhaging (Dengue Haemorrhagic Fever) and/or very low blood pressure (Dengue Shock Syndrome). This may be dramatic and mortality is high (50% without treatment). This occurs mainly in children. The cause of this serious course is not an infection with a more virulent virus. Dengue infection leads to the development of circulating antibodies. These mainly protect against the serotype involved (“neutralising” antibodies). However, sometimes these antibodies enhance virus multiplication and cause an increase in the severity of disease following symptoms infection with a different serotype. After infection there is probably life-long immunity against the serotype which caused the infection. In DHF, one can expect :

• fever

• haemorrhagic complications or positive tourniquet test

• thrombocytopenia <>

• signs of plasma loss such as pleural fluid, ascites, hypoproteinaemia, an increase in the haematocrit to > 20% above normal or a drop in the haematocrit of > 20% after hydration.

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The severity of the condition (DHF/DSS) can be given by a clinical score:

• Grade 1: thrombocytopenia (<100,000/µl>20% of the starting value)

• Grade 2: idem as 1 + spontaneous haemorrhages or positive tourniquet test

• Grade 3: idem as 1 or 2 + hypotension

• Grade 4: idem as 3 but the blood pressure is not measurable

Category: Medicine Notes