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[Microbiology](https://durgical.com/en/microbiology/) · [Viruses](https://durgical.com/en/microbiology/#d-virus)

# Other viruses and prions

- Viruses

Childhood respiratory viruses, haemorrhagic fevers, rodent-borne viruses, mosquito-borne encephalitis and prions, which are not viruses.

Updated 2026-11-01

## What they are

Seven groups of viruses that complete the syllabus (parainfluenza, metapneumovirus, filoviruses, hantaviruses, arenaviruses, equine encephalitis viruses and West Nile virus) plus prions. Prions sit here only by teaching tradition: they are misfolded proteins with no nucleic acid, not viruses, which is why they survive routine sterilisation.

## What they share

- Every virus in the group has an RNA genome and an envelope
- Many are zoonoses: bats (filoviruses), rodents (hantaviruses, arenaviruses), birds and horses (mosquito-borne viruses)
- For almost all of them treatment is supportive; few specific antivirals exist
- Prions have no nucleic acid and no envelope and trigger no inflammatory response

## Key points

- Croup (barking cough, stridor, steeple sign): parainfluenza virus.
- Ebola and Marburg: contact with blood and body fluids; strict isolation with full protective equipment.
- Hantavirus in the Americas: pulmonary syndrome from inhaled rodent excreta; in Europe and Asia, haemorrhagic fever with renal syndrome.
- Venezuelan equine encephalitis: horses amplify the virus; a large epidemic hit La Guajira in 1995.
- Prions are not viruses; routine sterilisation is not enough and neurosurgical instruments need a special protocol.

## Microorganisms in this group

- [**Parainfluenza virus** A common respiratory virus that gives young children croup: barking cough, hoarseness and noisy breathing from an inflamed larynx. Exam priority: medium](https://durgical.com/en/microbiology/parainfluenza-virus/)
- [**Human metapneumovirus** A respiratory virus related to RSV: it causes colds, bronchiolitis and pneumonia, mostly in young children, older adults and the immunocompromised. For completeness](https://durgical.com/en/microbiology/human-metapneumovirus/)
- [**Ebola and Marburg viruses (filoviruses)** Thread-shaped viruses that cause severe haemorrhagic fevers; they jump from bats to humans and then spread through a patient's blood and body fluids. Exam priority: medium](https://durgical.com/en/microbiology/ebola-and-marburg-viruses/)
- [**Hantavirus** Viruses of wild rodents caught by breathing dust laden with their urine or droppings; in the Americas they cause a severe pulmonary syndrome. For completeness](https://durgical.com/en/microbiology/hantavirus/)
- [**Arenaviruses (Lassa and the South American haemorrhagic fevers)** Rodent-borne viruses that cause haemorrhagic fevers: Lassa in West Africa and Junín, Machupo, Guanarito and Sabiá in South America. For completeness](https://durgical.com/en/microbiology/arenaviruses/)
- [**Equine encephalitis viruses and Mayaro virus** Mosquito-borne alphaviruses that cause fever and sometimes encephalitis in horses and people; Mayaro causes fever with joint pain. For completeness](https://durgical.com/en/microbiology/equine-encephalitis-viruses-and-mayaro-virus/)
- [**West Nile virus** A bird flavivirus spread by Culex mosquitoes; most infected people have no symptoms, but a few develop meningitis or encephalitis. For completeness](https://durgical.com/en/microbiology/west-nile-virus/)
- [**Prions** Not viruses: misfolded proteins that bend normal ones out of shape and destroy the brain; they survive routine sterilisation. Exam priority: medium](https://durgical.com/en/microbiology/prions/)

## Test yourself

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

## Why are prions not considered viruses?

They are misfolded proteins with no nucleic acid, capsid or envelope; they spread by making the normal protein change shape.

## Which reservoir do hantaviruses and arenaviruses share?

Rodents, which shed the virus in urine, faeces and saliva without becoming ill.

## Which virus of the group most often causes croup in young children?

Parainfluenza virus.

## What role do horses play in Venezuelan equine encephalitis and in West Nile virus?

In Venezuelan equine encephalitis they amplify the virus for mosquitoes; in West Nile they are dead-end hosts, like humans, and birds are the reservoir.

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

Sources: [About Viral Hemorrhagic Fevers | Viral Hemorrhagic Fevers (VHFs) | CDC](https://www.cdc.gov/viral-hemorrhagic-fevers/about/index.html) (CDC, 2024); [About Prion Diseases | Prions | CDC](https://www.cdc.gov/prions/about/index.html) (CDC, 2024); [About Human Parainfluenza Viruses | HPIVs | CDC](https://www.cdc.gov/parainfluenza/about/index.html) (CDC, 2024).

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Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/microbiology/groups/other-viruses-and-prions/