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What are Parainfluenza and Croup?

The human parainfluenza viruses (HPIVs) are a group of viruses that cause upper and lower lung infections. Parainfluenza viruses are a common cause of cold symptoms. It is also the major cause of croup in children.   

Croup is a sudden swelling of the upper airway that is caused by parainfluenza virus type 1 infection. Most symptom of croup is a bark-like cough or high-pitched sound when breathing in (inspiratory stridor), often occurring at night. This is a sign that the airway is partially blocked. Once infected with the virus it can take 2 to 7 days for symptoms to show. This virus most commonly arises in the spring, summer, and fall.

What causes parainfluenza infection? 

There are 4 different types of parainfluenza viruses in children and adults. Type 1 and 2 (HPIV-1, HPIV-2) are most associated in children and cause croup. Bronchiolitis, bronchitis, and pneumonia are caused by type 3 (HPIV-3) and type 4 (HPIV-4) and are less common. The virus spreads by being in contact with someone who is infected.

Is parainfluenza contagious? 

Yes, it can be spread from coughing and sneezing, direct person-to-person contact, by touching common surfaces and objects that have the virus on them. Therefore, it is important to avoid touching your mouth, nose, and eyes to prevent the virus from spreading. 

Signs and Symptoms 

Most children will get better at home within 3-7 days of symptoms starting. It is quite common for symptoms to become worse at night and may even wake your child up. 

Symptoms may consist of: 

  • Sore throat 
  • Frequent cough that sounds like a seal barking  
  • Hoarse voice  
  • Fever 
  • Runny or stuffy nose 
  • Chest pain 
  • Shortness of breath 
  • Wheezing 
  • Sneezing 
  • Ear pain 
  • Irritability 
  • Decreased appetite  

Croup signs & symptoms include: 

  • Frequent cough that sounds like a seal barking  
  • High-pitched sound when breathing in (inspiratory stridor), often occurring at night 
  • Hoarse voice 
  • Fever 

Children with worsening symptoms should be seen immediately in the emergency room and may need to stay in the hospital for observation and care. Prolonged duration of croup symptoms may be seen with secondary bacterial infection or indicate an additional underlying cause.  

Call 911 if your child has any of these warning signs: 

  • Unusual tiredness 
  • Trouble breathing 
  • Fast heartbeat 
  • Bluish tint to lips or fingers 
  • Unable to speak 
  • Unable to swallow  
  • Drooling 


Parainfluenza and croup are often diagnosed by observing the symptoms you are experiencing. A bark-like cough and high-pitched sound when breathing in (inspiratory stridor) are common signs of croup. Your health care provider will also listen to your lungs with a stethoscope. A throat or nasal swab may be taken to determine which virus is causing croup symptoms (most often this is parainfluenza).  

Other tests such as blood work, a chest x-ray, or a CT scan of the chest may be done to rule out other causes, but are often not necessary.  


There is no specific treatment or vaccine for parainfluenza infections. Most infections are mild and recovery takes place at home. There are several home treatments that may help with cold and croup-like symptoms. Medical intervention may be necessary if breathing difficulties develop.  

Home treatments may include: 

  • Keep your child calm: crying can make croup symptoms worse 
  • Keep hydrated: Encourage your child to drink plenty of water or provide popsicles 
  • Rest and sit upright: to help breathe easier 
  • Taking your child outside in cooler weather for a few minutes can help ease symptoms 
  • Inhaling steam or mist from a humidifier to help relieve coughing  
  • Saline nasal drops, rinses, or suctioning to clear the nose 
  • Keep your child away from smoke 
  • Use over-the-counter medications to relieve symptoms.  
  • Acetaminophen (Tylenol) or ibuprofen (Advil, Motrin) for fever, pain, or fussiness. Talk to your doctor or pharmacist to see which might work best for you or your child. 

Treatment of severe croup symptoms may include a steroid medicine to reduce airway swelling and sometimes breathing medications are given to help open up the airway. 

Take precautions with other medications: 

  • Most decongestants are not suitable for children under 6 years old. 
  • No antihistamines should not be given to children under 2 years old. 
  • Aspirin is not recommended for children under 12 because it increases the risk of Reye syndrome, which is a rare but life-threatening disorder. 


There are no vaccines currently available to protect against parainfluenza viruses. There are several actions you can take to limit the risk of infection and passing it along. 

  •  Wash your hands often 
    • One of the best preventive measures against viruses and other germs is practicing good hand hygiene. Because many viruses are spread through contact with the droplets of an infected person, washing your hands frequently with soap and water for at least 20 seconds is helpful to prevent catching a virus.  
  • Disinfect commonly touched surfaces 
    • It is recommended to clean all shared items and surfaces with disinfectants often to reduce the spread of the virus.  
  • Keep your distance 
    • If you have cold symptoms, it is best to stay home so you don’t get others sick. At home, try to keep your distance from other members of the household or wear a mask inside. When possible, sleep in a separate room. Keep infants who are sick away from any with the virus, due to their lowered ability to fight off germs. Limit exposure to large crowds as well.  
  • Wear masks 
    • Wearing a mask in crowded spaces can help prevent viruses from being spread. If you have to seek medical attention, ensure you are wearing a mask when leaving your home. 
  • Follow coughing and sneezing etiquette 
    • Sneeze and cough into a tissue and then throw it into the trash. If you do not have any tissues, cough or sneeze on the inside of your elbow, not your hands. After touching your nose or mouth you immediately wash your hands. 

Viral Infections & Lung Disease 

Viral infections can cause a flare-up or worsen symptoms for people with lung diseases such as asthma, COPD, and pulmonary fibrosis. Mucous can build up inside the airways causing irritation and worsening symptoms of your lung disease.  

  • If you have asthma, follow the advice in your asthma action plan or your child’s asthma action plan. If you have COPD, follow the advice in your COPD action plan. You may have to take extra medications to control your symptoms. If you do not have an action plan, work with your doctor to create one.  
  • If your symptoms are out of control or you don't know how to treat your lung disease, see your doctor as soon as possible.   
  • Watch for warning signs of severe symptoms as listed above. If you have these warning signs, get emergency help right away. Call your doctor if you are not improving after a few days.  
  •  If it's hard to breathe or your rescue medicine isn't working, call 911 or your local emergency number.