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Haemorrhagic fever

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Dengue

Viral Haemorrhagic fevers

Ross Calcroft

Overview

  • endemic on almost every continent except Australia
  • characterised by abrupt onset of high fever and in some cases, high mortality
  • the bleeding is a complication only of severe disease but the pathology is of widespread leakage form the capillaries with prominent pulmonary oedema
  • clinical syndrome is mainly caused by endothelial dysfunction
  • death is usually due to hypovolaemic shock, with or without ARDS
  • in survivors recovery is rapid and complete
  • caused by many different RNA viruses; almost all are zoonoses, and infection of humans is an accident.
  • There are four main families
    • Bunyaviridae
      • Crimean Congo haemorrhagic fever (CCHF): ticks; Africa, SE Europe, Middle East, and Asia
    • Hantavirus: everywhere; natural silent infections of rodents.
    • Arenaviridae
      • natural infections of rodents; Lassa fever is most important-W Africa
    • Filoviridae
    • Flaviviridae
      • yellow fever virus and dengue virus (mosquitos).

History and clinical diagnosis:

  • incubation period is a maximum of four weeks prior to the onset of fever
  • questions must include a recent travel history, information on any possible contact with ticks, fresh animal blood, rodent urine or blood, wild animals, and mosquitos and other insects; recent camping in exotic areas; possible entry into bat caves; attendance at ceremonial funerals; all these usually in remote areas.
  • essential element is a short history of fever, usually high and abrupt.
  • severe body pains, and headache and may be excruciating
  • other features may include sore throat, nausea and vomiting, petechiae, oozing from the gums, and bradycardia.
  • investigations: proteinuria is frequent; peripheral WCC are unhelpful, and neutrophilia may mislead.
  • thrombocytopaenia is usual, and platelet function is impaired; appt may be prolonged, but PT are usually normal.
  • DIC is not a feature except in the terminal phase
  • as disease progresses, hypovolaemic shock, pulmonary oedema, and frank bleeding ensue.
  • AST is usually disproportionately raised compared to ALT; ratio of up to 11:1, and the level of the AST also reflects prognosis
  • patients are rarely jaundiced, except in yellow fever.
  • CNS is relatively spared, but encephalopathy and neurologic sequelae such as ataxia and deafness occur.

Laboratory diagnosis

  • care with specimens
  • diagnosis is by virus isolation; demonstration of a fourfold rise in Ab titre; or high titre IgG antibody with virus specific IgM antibody in association with compatible clinical disease.
  • techniques include immunofluorescence and ELISA for detection of both antibody and antigen.
  • recently molecular techniques such as polymerase chain reactions (PCR) for detection of viral RNA have been found to be rapid, reliable, an safe to perform directly on serum or tissues.

Management

  • VHFs are self-limiting and providing the acute crises can be managed, recovery is rapid and complete
  • main challenge is careful management of fluid balance; pulmonary oedema is a real risk
  • blood and platelet infusions may be necessary
  • some viruses are highly treatable using the antiviral agent ribavarin, provided therapy is started as soon as possible
  • exchange transfusion and steroids are controversial and are not currently recommended
  • early accurate diagnosis and intensive therapy are the cornerstones of good management

Prevention of spread

  • strict isolation of febrile patients at risk of VHF and rigorous use of gloves and disinfection
  • high risk of infection is associated with direct percutaneous or mucosal contact with blood or body fluids, and post-exposure prophylaxis with ribavarin for CCHF and for arenaviruses, especially Lassa fever, should be offered to contacts with such exposures.

© Ross Calcroft November 1999

 

©Charles Gomersall, January, 2018 unless otherwise stated. The author, editor and The Chinese University of Hong Kong take no responsibility for any adverse event resulting from the use of this webpage.
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