What is croup?

Croup is an infection that affects the upper portion of the airway, including the larynx (voice box) and trachea (windpipe). It’s common in young children between the ages of 6 months and 3 years. It tends to occur in the fall months.

Common symptoms of croup include:

  • a barking cough
  • high-pitched or noisy breathing (stridor)
  • hoarseness or losing your voice
  • low-grade fever
  • runny or stuffy nose

The symptoms of croup are often worse in the evening or when a child is anxious or crying. They usually last for three to five days, though a mild cough may linger for up to a week.

Croup is contagious. But how contagious is it to adults? Is it more contagious between children? Read on to find out.

What causes croup?

Croup is most often caused by a viral infection, typically by a type of virus called a parainfluenza virus. Other viruses that can cause it include:

  • enteroviruses
  • rhinoviruses
  • influenza A and B viruses
  • respiratory syncytial virus

In rare rare cases, a bacteria can cause croup. This type of croup is often more severe than viral types.

How is it spread?

Croup is contagious, meaning that it can be spread from person to person. The pathogens that cause croup are spread by inhaling respiratory droplets that are produced when someone with croup coughs or sneezes.

In addition, coming into contact with contaminated surfaces, such as doorknobs or faucet handles, and then touching the face, nose, or mouth can spread the infection.

Is croup contagious to adults?

Teenagers sometimes develop croup, but it’s very rare in adults. Adult airways are larger and more developed than those of children. As a result, they might come into contact with the virus and possibly become infected, but it won’t cause the same breathing issues that it does in children.

If an adult does develop croup symptoms, they’re usually mild and include a light cough or sore throat. However, some adults may develop more severe breathing symptoms and require hospitalization. Again, this is very rare.

As of 2017, there were only 15 reported cases of adult croup in medical literature, though the true incidence is not known. Read more about croup in adults.

How long is it contagious?

A person with croup is usually contagious for about three days after symptoms start or until their fever disappears.

If your child has croup, it’s best to keep them home from school or other environments with lots of children for at least three days. You should also keep them home as long as they have any kind of fever.

Is croup preventable?

You can reduce your or your child’s risk of developing croup by washing your hands often and keeping hands away from your face. If someone around you has croup, try to limit your interaction with them until they’ve recovered.

If you or your child already has croup, it’s still a good idea to frequently wash your hands to avoid spreading it to others. It’s also helpful to cough or sneeze into a tissue.

There are also vaccines available for some bacterial infections that cause illnesses similar to severe croup. These include the Haemophilus influenzae type b (Hib) vaccine and the diphtheria vaccine.

Making sure that both you and your child receive these vaccines can protect against these more serious infections.

The bottom line

Croup is a contagious condition that tends to only affect children. Most cases are caused by a virus.

While a child can pass the virus to an adult, the virus usually doesn’t affect adults the same way that it does children. This is because adult airways are larger and are less susceptible to airway issues.

However, croup can spread easily between children, so it’s best to keep them at home for at least three days or until they no longer have a fever.