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Quick Facts on Viral Hemorrhagic Fevers

  • Viral Hemorrhagic Fevers (VHF) are caused by 4 viral families
    • Arenaviruses
      • Argentine hemorrhagic fever
      • Bolivian hemorrhagic fever
      • Sabia-associated hemorrhagic fever
      • Lassa fever
      • Lymphocyctic choriomeningitis
      • Venezuelan hemorrhagic fever
    • Filoviruses
      • Ebola hemorrhagic fever
      • Marburg hemorrhagic fever
    • Bunyaviruses
      • Crimean-Congo hemorrhagic fever
      • Rift Valley fever (Hantaan fever)
      • Hantavirus Pulmonary Syndrome
      • Hemorrhagic Fever with Renal Syndrome (HFRS)
    • Flaviviruses
      • Tick-borne encephalitis
      • Kyasanur Forest disease
      • Omsk hemorrhagic fever
  • Viral hemorrhagic fevers share the following characteristics:
    • They are all RNA viruses
    • They are all zoonotic (natural reservoir is an arthropod or other animal host)
    • Disease is restricted to habitat of the host
    • Humans become infected by contact with host
    • Some viruses can be transmitted from human to human
  • Transmission to humans (depends upon specific virus)
    • By contact with rodent urine, feces, saliva, blood
    • From mosquito or tick bites
    • Contact with vector-infected livestock
  • Pathophysiology
    • The target organ is the vascular bed. Dominant clinical features are due to microvascular damage and changes in vascular permeability
    • In most cases of viral hemorrhagic fever, the coagulopathy is multifactorial, including: hepatic damage, disseminated intravascular coagulation, primary marrow injury to megakaryocytes
  • Symptoms
    • Fever, fatigue, dizziness, myalgias, and prostration
    • Signs of bleeding range from only conjunctival hemorrhage, mild hypotension, flushing, and petechiae to shock and generalized mucous membrane hemorrhage and evidence of pulmonary, hematopoietic, and neurologic dysfunction
    • Renal insufficiency is proportional to cardiovascular compromise except in Hemorrhagic Fever and Renal Syndrome in which it is an integral part of the disease
  • Clinical syndromes
    • Epidemiologic information is usually the most helpful clue to the diagnosis, although some viral hemorrhagic fevers do present with suggestive clinical syndromes
      • Jaundice and hepatitis dominate the clinical presentation in some cases of Rift Valley, Congo-Crimean, Marburg, and Ebola hemorrhagic fevers, and yellow fever
      • Biphasic illnesses with pulmonary symptoms followed by central nervous system manifestations are characteristics of Kyasanur Forest disease and Omsk hemorrhagic fever
      • Severe peripheral edema without significant hemorrhage suggests Lassa fever
      • Severe hemorrhage and nosocomial transmission suggests Congo-Crimean hemorrhagic fever
      • Fever, hemorrhage, shock, renal failure, and polyuria is the classic presentation of Hemorrhagic Fever and Renal Syndrome
      • Adult Respiratory Distress Syndrome is a sequela of Hantavirus
  • Diagnosis
    • Key is a detailed travel history and a high index of suspicion
      • Suspect viral hemorrhagic fever in any patient who has traveled to an endemic area and has a severe febrile illness with evidence of vascular involvement
    • Consider the possibility of a bioterrorist attack if one of the diseases occurs in persons not known to have traveled to an endemic area
    • Laboratory findings
      • Thrombocytopenia is common to most viral hemorrhagic fever infections with the exception of Lassa fever
      • Leukopenia is common to most viral hemorrhagic fever infections with the exceptions of Lassa, Hantaan, and some cases of Congo-Crimean hemorrhagic fevers
      • Proteinuria with or without hematuria is common and is always found in Argentine hemorrhagic fever, Bolivian hemorrhagic fever, and Hemorrhagic Fever and Renal Syndrome
      • Virologic diagnosis
        • Rapid enzyme immunoassays
        • Viral culture (requires 3 to 10 days)
  • Differential Diagnosis
    • The major entity in the differential diagnosis is malaria
    • Other entities that mimic viral hemorrhagic fevers include typhoid fever, leptospirosis, rickettsial infections, shigellosis, relapsing fever, fulminant hepatitis, and meningococcemia
    • Noninfectious mimics include acute leukemia, systemic lupus erythematosus, immune thrombocytopenic purpura, thrombotic thrombocytopenic purpura, and hemolytic uremic syndrome
  • Treatment
    • For most viral hemorrhagic fevers, there is no effective treatment other than supportive care.
    • Ribavirin, which is available via compassionate use protocols, reduces morbidity in Hemorrhagic Fever and Renal Syndrome, and reduces morbidity and mortality in Lassa fever
    • Convalescent plasma is being used experimentally to treat Argentine hemorrhagic fever
  • Prevention
    • Vaccination
      • The only licensed vaccine available is for yellow fever
      • Experimental vaccine for Argentine hemorrhagic fever is under investigation
    • Control of rodent populations
    • Control of insect and other arthropod populations
  • Isolation and containment
    • Viral hemorrhagic fever patients, with the exception of hantavirus and dengue fever infections, have significant infectious virus in the blood and body secretions
    • Strict adherence to standard precautions
      • Keep patients in isolation
      • Use of gowns, gloves, masks, eye protection
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