Parainfluenza viruses cause upper and lower respiratory infections.

Causes, incidence, and risk factors 

There are four types of Parainfluenza virus, all of which can cause upper respiratory infections or lower respiratory infections (Pneumonia) in adults and children. The virus is especially important in children because it is responsible for approximately 40-50% of croup cases and 10-15% of Bronchiolitis and Bronchitis cases and some Pneumonias.

The exact number of cases of parainfluenza is unknown but suspected to be very high. Sometimes the viruses cause only a runny nose and other symptoms that may be diagnosed as a simple cold rather than parainfluenza.

Risk factors for parainfluenza include young age. By school age, most children have been exposed to parainfluenza virus. Most adults have antibodies against parainfluenza although they can get repeat infections.

Symptoms vary depending on the type of infection. Cold-like symptoms consisting of a runny nose and mild cough are common. Life-threatening respiratory symptoms can be seen in young infants with Bronchiolitis. For detailed symptoms see the specific disease.

Signs and tests 

  • sinus tenderness  
  • red throat  
  • swollen glands at neck  
  • crackles or wheezing in lungs  
  • fever


  • swab of nose for rapid viral test  
  • viral culture (very expensive; cultures generally are not performed for reasons other than to determine the nature of an epidemic)  
  • CBC  
  • arterial blood gases

There is no specific treatment for the viral infection. Specific treatments are available for the symptoms of croup and Bronchiolitis.

Expectations (prognosis) 
Most infections in adults and older children are mild and recovery takes place without treatment, unless the person is very old or has an abnormal immune system. Medical intervention may be necessary if breathing difficulties develop.

Secondary bacterial infections are the most common complication. Airway obstruction in croup and Bronchiolitis can be severe, even life-threatening.

Calling your health care provider 
Call your health care provider if your child develops croup, Wheezing or any other type of breathing difficulty. You may wish to call your health care provider for children under 18 months of age with any type of upper respiratory symptoms.


There are no vaccines available for parainfluenza. Infections are most common in fall and winter. Avoiding crowds to limit exposure during peak outbreaks may decrease the likelihood of infection.

Parainfluenza infections are most severe in infants and become less severe with age. Limiting exposure, such as occurs in day-care centers and full nurseries, may delay infection until the child is older.

Johns Hopkins patient information

Last revised: December 3, 2012
by Levon Ter-Markosyan, D.M.D.

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