Rift valley fever: Difference between revisions
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==Clinical Features==
==Clinical Features==
*Incubation period of 2-6 days
*Incubation period of 2-6 days
*Several different disease syndromes
===Mild===
**Mild RVF
*No symptoms or flu-like illness (fever, myalgias, joint pain, headache)
***No symptoms or flu-like illness (fever, myalgias, joint pain, headache)
*Early disease can be mistaken for meningitis with occasional neck stiffness and sensitivity to light
***Early disease can be mistaken for meningitis with occasional neck stiffness and sensitivity to light
*Resolves within 1 week
***Resolves within 1 week
 
**Severe RVF
===Severe===
***Occular form- 0.5-2% of patients
*Occular form- 0.5-2% of patients
****Mild disease form + retinal lesions, blurred and decreased vision
**Mild disease form + retinal lesions, blurred and decreased vision
****Retinal lesions occur 1-3 weeks after disease onset and last 10-12 weeks
**Retinal lesions occur 1-3 weeks after disease onset and last 10-12 weeks
****50% of patients with macular lesions will develop permanent vision loss
**50% of patients with macular lesions will develop permanent vision loss
***Meningoencephalitis form- <1% of patients
*Meningoencephalitis form- <1% of patients
****Severe headache, memory loss, hallucinations, confusion, vertigo, seizures, coma, and late neurological complications
**Severe headache, memory loss, hallucinations, confusion, vertigo, seizures, coma, and late neurological complications
****Onset is 1-4 weeks after mild symptoms
**Onset is 1-4 weeks after mild symptoms
****Residual severe neurological deficits are common
**Residual severe neurological deficits are common
***Hemorrhagic fever form- <1% of patients
*Hemorrhagic fever form- <1% of patients
****Jaundice is first sign due to liver dysfunction
**Jaundice is first sign due to liver dysfunction
****Hemorrhage (vomit, stool, gums, menorrhagia), purpuric rash, echymosis
**Hemorrhage (vomit, stool, gums, menorrhagia), purpuric rash, echymosis
****Onset is 2-4 days after illness, death in 3-6 days
**Onset is 2-4 days after illness, death in 3-6 days
****Most fatalities from RVF, 50% fatality rate
**Most fatalities from RVF, 50% fatality rate


==Differential Diagnosis==
==Differential Diagnosis==

Revision as of 02:40, 10 June 2015

Background

  • Viral illness caused by RVF virus, a bunyaviridae
  • Primarily infects domesticated animals; cattle, sheep, buffalo, etc.
  • Outbreaks related to unusually heavy rainfall and flooding
  • Found mostly in eastern and southern Africa where domesticated animals are raised
    • Can be found in most of Africa
    • Recent outbreaks in Saudi Arabia and Yemen (first outside African continent)
  • Outbreaks cause major economic impact with livestock death

Transmission

  • Mosquitos, most commonly Aedes, are a reservoir and vector for RVF virus
    • Able to live with the virus and pass on to offspring, virus remains viable in eggs
    • Bite livestock and humans to cause infection
    • Increased rainfall increases mosquito numbers and is associated with outbreaks
  • Humans are most commonly infected through direct contact of blood or other bodily fluids of infected livestock
    • Slaughter, veterinary procedures, obstetrical procedures
  • No documented human to human transmission
  • Aerosolized transfer has occurred in laboratory settings

Clinical Features

  • Incubation period of 2-6 days

Mild

  • No symptoms or flu-like illness (fever, myalgias, joint pain, headache)
  • Early disease can be mistaken for meningitis with occasional neck stiffness and sensitivity to light
  • Resolves within 1 week

Severe

  • Occular form- 0.5-2% of patients
    • Mild disease form + retinal lesions, blurred and decreased vision
    • Retinal lesions occur 1-3 weeks after disease onset and last 10-12 weeks
    • 50% of patients with macular lesions will develop permanent vision loss
  • Meningoencephalitis form- <1% of patients
    • Severe headache, memory loss, hallucinations, confusion, vertigo, seizures, coma, and late neurological complications
    • Onset is 1-4 weeks after mild symptoms
    • Residual severe neurological deficits are common
  • Hemorrhagic fever form- <1% of patients
    • Jaundice is first sign due to liver dysfunction
    • Hemorrhage (vomit, stool, gums, menorrhagia), purpuric rash, echymosis
    • Onset is 2-4 days after illness, death in 3-6 days
    • Most fatalities from RVF, 50% fatality rate

Differential Diagnosis

Fever in traveler

Workup

  • Pursue other possible causes of fever
  • IgM ELISA, viral detection, and RT-PCR can be used to diagnose acute infection. IgG ELISA for previous infection.

Management

  • Mild disease syndromes require no intervention and are self limited
  • No specific treatment exists for severe disease forms
    • Supportive Care
      • Pain control
        • DO NOT use ASA in hemorrhagic form
    • IVFs
    • Blood Component Transfusion - consider in hemorrhagic shock
  • Inactivated vaccine has been developed for humans
    • Not licensed and not commercially available
    • Experimental use on veterinary and lab workers
  • Approved vaccines for livestock

Disposition

  • Isolation precautions: standard, contact, and consider droplet
  • Admit if severe form suspected, likely ICU
    • Consult ID
    • Consult ophthalmology for ocular form

See Also

Sources

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