Is Croup Contagious?

Croup is a contagious upper respiratory tract infection causing airway swelling and a hoarse, barking-like cough. Croup is most common in children between the ages of 3 months old and 5 years old, but older children can also become infected with croup.

This article will explore how long croup is contagious. It will also provide more detail on how children contract croup, how to prevent croup from spreading in your home and community, signs of croup improving worsening, and when to seek medical care.

How Long Is Croup Contagious?

Croup is contagious in the first few days after the onset of symptoms and when fever is present. Symptoms typically last between three and five days.

Croup can be passed among children and from a child to an adult.

Symptoms of croup include:

• Cold symptoms, including runny nose and fever
• Upper airway inflammation and swelling in the first 12–48 hours
• Cough that sounds like seal barking (raspy and hoarse)
  
• Increased breathing rate
• High-pitched squeaky or crowing noise when breathing (stridor) in more moderate to severe cases

After Treatment

With fever, you are considered contagious until the fever breaks, resolves, or is gone without return. Symptoms after treatment may no longer be contagious but can still occur. For example, coughing symptoms can persist for weeks after the infection clears.

Without Fever

While most children develop a fever with croup, some children will never get one. Without fever, symptoms are considered contagious for the first three days.

How Do Children Get Croup?

In most cases, croup is caused by viruses. Common viruses that can lead to croup infection include:

• Human parainfluenza virus (HPIVs)
• Respiratory syncytial virus (RSV)
• Influenza virus
• Adenovirus
• Enteroviruses

Most children get croup from breathing in respiratory droplets spread by sneezing, coughing, wheezing, or crying.

Adults often get croup from being in close contact with children who are contagious with the croup infection. In rare cases, croup is linked to allergies, bacteria, or acid reflux from the stomach.

How to Keep Croup From Spreading to Others

To prevent the spread of croup, children with symptoms should not go to school or daycare for the first three days after onset of symptoms or until fever resolves.

Other methods of preventing the spread of croup to others include:

• Practice proper hand hygiene (frequent and thorough hand washing and drying).
• Teach children how to cough into their elbows instead of their hands.
• Stay up-to-date on the latest vaccinations that can help prevent some respiratory illnesses.
• Follow your healthcare provider’s treatment protocol, which may include medications.

Signs Croup Is Improving: When to Resume Normal Activity

Only you and your healthcare provider can determine when to resume regular activity after croup. Normal activity includes returning to daycare or school.

Signs Croup Is Getting Worse

Croup will get worse before it gets better. While croup begins with cold-like symptoms, it progresses to the barking-cough characteristic of croup and breathing difficulties.

It is important to look out for stridor, a high-pitched breathing sound caused by abnormal airflow. If this occurs, it is a sign the croup is getting worse. Experts say symptoms can worsen during nighttime and when a child is upset and crying. If stridor occurs when a child is at rest (that is, when not crying or coughing), it is a sign of an emergency.

Less than 5% of children with croup require hospitalization. Even in these cases, croup hospitalization is typically no more than a few hours to two days.

When to Seek Immediate Medical Care

Complications with croup are not common. Experts recommend calling 911 or going directly to the nearest emergency room if the child with a croup infection experiences the following symptoms:

• Stridor at rest
• Pale, bluish, or grayish skin around mouth and face 
• Skin around mouth or fingernails starts turning blue when coughing
• Not being able to catch their breath
• Drooling or cannot swallow
• Excessive tiredness or difficulty waking up
• Signs of dehydration (no tears while crying, peeing less, sunken eyes)

Summary

Croup is a viral infection in children usually under 5 years old. Croup can spread among children and from children to adults. The virus in mucus or respiratory droplets spreads through sneezing, coughing, crying, and wheezing. The croup infection is contagious until three days after symptoms start or, if fever is present, until the fever resolves.

Signs that the infection is getting worse include increased breathing difficulties like stridor. Severe and rare cases may include a pale or bluish tone to the skin around the mouth and fingernails. When in doubt, try to remain calm and consult your healthcare provider.