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Parainfluenza refers to a group of viruses that lead to upper and lower respiratory infections.


There are four types of parainfluenza virus, all of which can cause

or lower respiratory infections (pneumonia) in adults and children. The virus can cause , , and certain types of pneumonia.

The exact number of parainfluenza cases is unknown. The number is 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.

Infections are most common in fall and winter. Parainfluenza infections are most severe in infants and become less severe with age. By school age, most children have been exposed to the 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 and those with weakened immune systems.

In general, symptoms may include:

  • Chest pain
  • Cough
  • Croup
  • Fever
  • Runny nose
  • Shortness of breath
  • Sore throat
  • Stuffy nose
  • Wheezing

Exams and Tests

A physical exam may show sinus tenderness, swollen glands, and a red throat. The doctor will listen to the lungs and chest with a stethoscope. Abnormal sounds, such as crackling or wheezing, may be heard.

Tests that may be done include:

  • Arterial blood gases
  • Blood cultures (to rule out other causes of pneumonia)
  • Chest x-ray
  • CT scan of the chest
  • Complete blood count (CBC)
  • Swab of nose for rapid viral test
  • Blood cultures (to rule out other causes of pneumonia)


There is no specific treatment for the viral infection. Specific treatments are available for the symptoms of croup and bronchiolitis to make breathing easier.

Outlook (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.

Possible Complications

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

When to Contact a Medical Professional

Call your health care provider if you or your child develops croup, wheezing, or any other type of breathing difficulty. Contact your health care provider if a child under 18 months develops any type of upper respiratory symptom.


There are no vaccines available for parainfluenza. Avoiding crowds to limit exposure during peak outbreaks may decrease the likelihood of infection. Wash your hands often.

Limiting exposure to day care centers and nurseries may delay infection until the child is older.


Lee FE, Treanor J. Viral infections. In: Mason RJ, Broaddus CV, Martin TR, et al. Murray & Nadel's Textbook of Respiratory Medicine. 5th ed. Philadelphia, PA: Elsevier Saunders; 2010:chap 31.

Weinberg GA, Edwards KM. Parainfluenza viral disease. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 24th ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 371.

Version Info

  • Last reviewed on 8/30/2014
  • Denis Hadjiliadis, MD, Associate Professor of Medicine, Pulmonary, Allergy, and Critical Care, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.

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