[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Microbiology](https://durgical.com/en/microbiology/) › [Respiratory RNA viruses](https://durgical.com/en/microbiology/groups/respiratory-rna-viruses/) › Respiratory syncytial virus

[Microbiology](https://durgical.com/en/microbiology/) · [Respiratory RNA viruses](https://durgical.com/en/microbiology/groups/respiratory-rna-viruses/)

# Respiratory syncytial virus

- Virus
- Enveloped
- Contact
- Exam priority: medium

A virus that causes colds in adults and bronchiolitis in babies. It is the top reason infants are admitted to hospital with a respiratory infection.

Updated 2026-11-01

Also called: RSV

## Key points

- Negative-sense pneumovirus; protein F forms syncytia
- Leading cause of bronchiolitis and infant admissions
- Apnoea in very young infants
- Contact precautions
- Prophylaxis with anti-F monoclonal antibodies

## At a glance

**Shape**
Spherical or filamentous

**Genome**
Single-stranded, negative-sense, non-segmented RNA

**Envelope**
Enveloped

**Family**
Pneumoviridae, genus Orthopneumovirus

**Size**
Pleomorphic, about 150 nm or more (up to several hundred nm)

## Morphology

- Envelope with glycoprotein G (attachment) and protein F (fusion), which forms syncytia
- No haemagglutinin or neuraminidase
- Two subgroups, A and B

## Transmission

- Contact with secretions on hands, toys and surfaces, where it survives for hours
- Respiratory droplets at short range
- Hospital outbreaks on paediatric wards

**Reservoir:** Humans

### Isolation precautions

What the care team adds to standard precautions.

**Contact**
Gown and gloves; dedicated equipment. For C. difficile, soap-and-water hand washing.

## Virulence factors

- Protein F fuses bronchiolar epithelial cells into syncytia
- Epithelial necrosis, mucus and oedema block the infant's small bronchioles
- Immunity after infection is incomplete: reinfection occurs throughout life

## Diseases it causes

- Bronchiolitis in infants [Bronchiolitis (RSV) →](https://durgical.com/en/conditions/bronchiolitis/)
- Pneumonia in infants, older adults and immunocompromised people

## Clinical picture

- Runny nose and poor feeding; cough 1 to 3 days later; then wheeze and breathing difficulty
- Under 6 months: apnoea, irritability or lethargy
- Higher risk in preterm infants, congenital heart disease and chronic lung disease
- In older adults: pneumonia and worsening of COPD, asthma or heart failure

## Diagnosis

- Clinical diagnosis of bronchiolitis in infants
- RT-PCR or antigen on a nasopharyngeal aspirate or swab when it changes care or for cohorting
- X-ray with hyperinflation and atelectasis, not essential

## Treatment

Supportive: oxygen, hydration, nasal suction and ventilation if needed. Bronchodilators and corticosteroids show no routine benefit in bronchiolitis; inhaled ribavirin is kept for exceptional cases in immunocompromised patients.

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

## Prevention

- Monoclonal antibodies against protein F for infants (nirsevimab; palivizumab in high-risk groups)
- Maternal prefusion F protein vaccine during pregnancy
- Vaccine for older adults in some countries
- Hand hygiene and contact precautions in hospital

## In Colombia

In Colombia RSV is the main cause of bronchiolitis and of respiratory admissions in children under two, with peaks in the rainy seasons that overload paediatric services.

## Memory aid

RSV "Really Seals Very small airways" with mucus and fused cells.

## Test yourself

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

## Which RSV protein forms syncytia and is the target of preventive antibodies?

The fusion protein F.

## Which precautions are used for an infant admitted with RSV?

Contact precautions (gown and gloves) on top of standard ones.

## Which warning sign can be the first feature of RSV in a very young infant?

Apnoea, sometimes before cough or wheeze appear.

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/microbiology/respiratory-syncytial-virus/)

## Related

- [Influenza virus](https://durgical.com/en/microbiology/influenza-virus/)
- [Rhinovirus](https://durgical.com/en/microbiology/rhinovirus/)

## Related conditions

- [Bronchiolitis (RSV)](https://durgical.com/en/conditions/bronchiolitis/)

## What the colours mean

**Gram-positive**
Thick peptidoglycan wall: stains purple.

**Gram-negative**
Thin wall with an outer membrane: stains pink.

**Acid-fast**
Lipid-rich wall (mycobacteria): Ziehl–Neelsen stain.

**Contact**
Gown and gloves; dedicated equipment. For C. difficile, soap-and-water hand washing.

**Droplet**
Surgical mask within about a metre; single room.

**Airborne**
N95 respirator and a negative-pressure room.

[← Back to the group: Respiratory RNA viruses](https://durgical.com/en/microbiology/groups/respiratory-rna-viruses/)

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

Sources: [Clinical Overview of RSV](https://www.cdc.gov/rsv/hcp/clinical-overview/index.html) (CDC, 2025); [Appendix A: Type and Duration of Precautions Recommended for Selected Infections and Conditions](https://www.cdc.gov/infection-control/hcp/isolation-precautions/appendix-a-type-duration.html) (CDC, 2024).

## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake

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/respiratory-syncytial-virus/