Croup is contagious. It can be passed from person to person easily but is most common in children and, occasionally, adolescents. It’s rarely seen in grown-ups, and when it does appear, the symptoms are usually mild.

Croup is a condition caused by 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 ages 6 months and 3 years. It tends to occur in the fall months.

Common symptoms of croup include:

  • 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 3 to 5 days, though a mild cough may linger for up to a week. If your child has any trouble breathing, seek medical attention immediately.

The infection that causes croup is contagious. But how contagious is it to adults? Is it more contagious between children? Read on to find out.

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

The infection that causes croup is contagious, meaning that it can be transmitted from person to person. The infection-causing agents (pathogens) are transferred 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.

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 develop an infection, but it will not 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.

Infectious agents that cause croup can be transferred for about 3 days after a person starts to show symptoms or until their fever disappears. The recommendation is to remain home until 24 hours without fever and without using fever-reducing medications.

If your child has croup, it’s best to keep them home from school or other environments with lots of children for at least 3 days. You should also keep them home as long as they have any kind of fever.

You can reduce your or your child’s risk of developing croup by washing your hands often, especially after sneezing, 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 also helpful to cough or sneeze into a tissue. Wash your hands frequently to avoid transferring it to others.

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. Only certain adults at high risk will qualify for the Hib vaccine.

Speak with your doctor or your child’s pediatrician to determine if and when these vaccines are needed.

Making sure that both you and your child receive these vaccines can protect against these more serious infections. Be sure to follow the routine vaccine schedules for adults and for children.

Croup is a 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 does not affect adults the same way that it does children. This is because adult airways are larger and are less susceptible to airway issues.

However, the viruses or bacteria that cause croup can be easily transmitted between children, so it’s best to keep them at home for at least 3 days or until they no longer have a fever.