What Is Croup Caused By?

Reviewed on 8/31/2021

Croup (laryngotracheobronchitis) is a viral respiratory illness that causes a barking cough. There are many viruses that can cause croup, including parainfluenza viruses, respiratory syncytial viruses (RSV), adenoviruses, enteroviruses, Human coronavirus NL63 (HCoV-NL63), rhinoviruses, herpes, and others.
Croup (laryngotracheobronchitis) is a viral respiratory illness that causes a barking cough. There are many viruses that can cause croup, including parainfluenza viruses, respiratory syncytial viruses (RSV), adenoviruses, enteroviruses, Human coronavirus NL63 (HCoV-NL63), rhinoviruses, herpes, and others.

Croup (laryngotracheobronchitis) is a viral respiratory illness characterized by high-pitched, noisy breathing (stridor), hoarseness, and barking cough.

Croup is highly contagious and commonly affects children ages six months to three years. The peak time for croup to occur is when a child is 2 years old. Croup affects younger children more often because younger children have smaller airways and even a small amount of swelling can make it hard for a baby or young child to breathe. 

Most cases of croup are caused by viruses

Viruses that cause croup include: 

  • Parainfluenza viruses
  • Respiratory syncytial viruses (RSV)
  • Adenoviruses 
  • Enteroviruses (especially Coxsackie types A9, B4, and B5, and echovirus types 4, 11, and 21)
  • Human coronavirus NL63 (HCoV-NL63) 
    • This is not the same coronavirus that causes COVID-19
  • Rhinoviruses
  • Herpes simplex viruses 
  • Metapneumoviruses 
  • Influenza viruses (uncommon)
  • Measles (in areas where measles remains prevalent)

Secondary bacterial infections may also occur, such as:

Croup can sometimes be caused by bacteria, including Mycoplasma pneumoniae. It may also occasionally be caused by allergies or reflux from the stomach.

What Are Symptoms of Croup?

The first symptoms of croup include: 

  • Congestion
  • Runny nose
  • Inflammation of the mucus membranes inside the nose (coryza)

After the early symptoms, croup progresses over 12 to 48 hours and symptoms include:

  • High-pitched, noisy breathing (stridor)
  • Cough that sounds like a barking seal
  • Hoarseness
  • Fever
  • Mild fast, shallow breathing 
  • Mild sore throat
  • Pneumonia (in severe cases)

The cough associated with croup tends to resolve in about three days but other symptoms may persist for up to a week and before gradually fading.

How Is Croup Diagnosed?

Croup is diagnosed based on a patient’s symptoms of high-pitched, noisy breathing (stridor) and barking cough, especially during a a period when one of the viruses that causes croup is active in the community. 

Tests may be used to rule out other conditions, such as:

  • Blood tests
    • White blood cell (WBC)
    • Blood urea nitrogen (BUN)
    • Serum bicarbonate 
  • Viral culture and/or rapid diagnostic tests that detect viral antigens 
  • Chest X-ray

What Is the Treatment for Croup?

Home remedies can be used to treat symptoms of mild croup and may include:

  • Drinking enough fluids
  • Humidifier/mist
  • Fever reducers 

A single dose of oral dexamethasone may also be prescribed to treat mild croup.

Treatment for moderate to severe croup includes: 

  • Nebulized epinephrine 
  • Dexamethasone or nebulized budesonide 
  • Supportive care
    • Drinking enough fluids
    • Humidified air or oxygen
    • Fever reducers 
  • Supplemental oxygen if needed

SLIDESHOW

Cold and Flu: Finding Relief for Your Cough  See Slideshow

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Reviewed on 8/31/2021
References
https://www.uptodate.com/contents/croup-clinical-features-evaluation-and-diagnosis?search=croup&source=search_result&selectedTitle=2~73&usage_type=default&display_rank=2

https://www.uptodate.com/contents/management-of-croup?search=croup&source=search_result&selectedTitle=1~73&usage_type=default&display_rank=1

https://www.cedars-sinai.org/health-library/diseases-and-conditions---pediatrics/c/croup-in-children.html