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Other bunyaviruses

  • Virus
  • Enveloped
  • ContactGown and gloves; dedicated equipment. For C. difficile, soap-and-water hand washing.
  • DropletSurgical mask within about a metre; single room.
  • For completeness

Viruses spread by mosquitoes, sandflies or ticks. They range from childhood encephalitis and summer meningitis to haemorrhagic fevers.

Updated

Also called: La Crosse virus, Toscana virus, sandfly fever viruses, Rift Valley fever virus, Crimean-Congo haemorrhagic fever virus, CCHF

Quick facts

Type
Virus · RNA arboviruses
Gram / shape
Spherical
Spread
La Crosse · Toscana and sandfly fever viruses · CCHF
Causes
La Crosse encephalitis · Sandfly fever
Treatment
Supportive care for all

At a glance

Shape
Spherical
Genome
Single-stranded, negative-sense (partly ambisense) RNA in three segments (L, M, S)
Envelope
Enveloped
Family
Order Bunyavirales: Peribunyaviridae (La Crosse), Phenuiviridae (Toscana, sandfly fever, Rift Valley fever), Nairoviridae (CCHF)
Size
About 80 to 120 nm

Morphology

  • Envelope with two glycoproteins (Gn and Gc) and three helical nucleocapsids
  • The segmented genome allows reassortment between related viruses
  • Unlike most family members spread by arthropods, hantaviruses (same order) come from rodents

Transmission

  • La Crosse: Aedes triseriatus (tree-hole mosquito) in the eastern and midwestern United States; chipmunks and squirrels amplify it
  • Toscana and sandfly fever viruses: Phlebotomus sandflies around the Mediterranean, April to November
  • Rift Valley fever: blood and organs of infected livestock (slaughter, birthing) and Aedes or Culex mosquitoes in Africa and Arabia
  • CCHF: Hyalomma tick bites or the blood of infected livestock in Africa, the Balkans, the Middle East and Asia
  • CCHF also spreads person to person through blood and body fluids, including in hospitals: contact and droplet precautions

Reservoir: Chipmunks and squirrels (La Crosse); Livestock and Aedes eggs (Rift Valley fever); Hyalomma ticks and livestock (CCHF); Sandflies (Toscana)

Vector: Aedes triseriatus (La Crosse); Phlebotomus sandflies (Toscana, sandfly fever); Aedes and Culex mosquitoes (Rift Valley fever); Hyalomma ticks (CCHF)

Isolation precautions

What the care team adds to standard precautions.

Contact
Gown and gloves; dedicated equipment. For C. difficile, soap-and-water hand washing.
Droplet
Surgical mask within about a metre; single room.

Virulence factors

  • La Crosse and Toscana are neurotropic, causing encephalitis or meningitis
  • Rift Valley fever virus targets the liver; a minority develop retinitis, encephalitis or haemorrhagic fever
  • CCHF virus damages endothelium and the liver and triggers coagulopathy, with bleeding and multiorgan failure

Diseases it causes

Clinical picture

  • La Crosse: fever, headache and vomiting; a few children develop seizures and encephalitis, with low mortality
  • Toscana: fever, headache and stiff neck; among the commonest causes of summer meningitis in southern Europe
  • Rift Valley fever: usually a flu-like illness; under 2% develop retinal lesions and under 1% haemorrhagic fever with about 50% fatality
  • CCHF: sudden fever, myalgia and photophobia, then petechiae, large bruises and bleeding; about 30% fatality, deaths in the second week

Diagnosis

  • RT-PCR on blood or CSF early in illness; IgM ELISA later
  • CCHF and Rift Valley fever samples are a biohazard needing maximum containment
  • Thrombocytopenia, leukopenia and raised liver enzymes in CCHF and Rift Valley fever
  • Neutralization tests sort out cross-reactions between related viruses

Treatment

Supportive care for all; there is no approved specific antiviral. Ribavirin has been used off-label for CCHF, but its benefit is uncertain.

Drug class only; doses and regimens are set by the clinician from the current guideline.

In Pharmacology:

Prevention

  • Mosquito and sandfly bite avoidance; remove tree-hole and container breeding sites (La Crosse)
  • Tick checks, repellents and light-coloured clothing in CCHF areas
  • Gloves and protective gear for slaughter, birthing and veterinary work; avoid raw milk
  • Barrier nursing and safe injection practices to prevent hospital spread of CCHF
  • Rift Valley fever: animal vaccines prevent outbreaks; no licensed human vaccine

Test yourself

Think of the answer, then tap the question to see it.

Which tick genus transmits Crimean-Congo haemorrhagic fever virus?

Hyalomma ticks.

Which bunyavirus is a frequent cause of summer aseptic meningitis in southern Europe?

Toscana virus, transmitted by Phlebotomus sandflies.

What eye complication is typical of Rift Valley fever?

Retinal lesions (retinitis) that can cause permanent vision loss if the macula is involved.

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Connections

← Back to the group: RNA arboviruses

Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: Crimean-Congo haemorrhagic fever (World Health Organization (WHO), 2022); Rift Valley fever (World Health Organization (WHO), 2023); About La Crosse Virus (CDC, 2024); Toscana virus infection (European Centre for Disease Prevention and Control (ECDC), 2023).

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Representative model, for educational purposes only.