What Is Parainfluenza?

Parainfluenza refers to a group of viruses called the human parainfluenza viruses (HPIV). There are four viruses in this group and each one causes different symptoms and illnesses. All forms of HPIV cause an infection in either the upper or lower respiratory area of the body.

Symptoms of HPIVs are similar to those of the common cold, and when cases are mild, the viruses are often misdiagnosed. Most healthy people who are infected with an HPIV recover with no treatment. On the other hand, a person with a weakened immune system is at risk for developing a serious and life-threatening infection.

The Four Types of Parainfluenza Viruses

There are four different types of HPIV. Although they all cause a respiratory infection, the exact type of infection, the symptoms, and the location of the infection depend on the type of virus you have. Anyone can be infected by any of the four types of HPIV.


HPIV-1 is the leading cause of croup in children. Croup is a swelling near the vocal chords and in other parts of the upper respiratory system. According to the Centers for Disease Control and Prevention (CDC) HPIV-1 is responsible for biennial outbreaks of croup in the autumn. In America, the outbreaks tend to be more widespread in odd-numbered years (CDC).


HPIV-2 also causes croup in children, but it is detected much less often than HPIV-1. It is seen mostly in the autumn, but to a lesser degree than HPIV-1.


An infection by HPIV-3 is mostly associated with bronchiolitis—which is swelling in the airways that leads to the lungs—and with pneumonia. It causes infections largely in the spring and early summer, but it can be seen in patients throughout the year.


There are two subtypes of HPIV-4: HPIV-4A and HPIV-4B. HPIV-4 is rarely included in screening panels for acute respiratory infections. This omission may be distorting our understanding of its prevalence and it role in serious respiratory infections. Any pattern in HPIV-4 outbreaks is currently unknown.

How Is Parainfluenza Transmitted?

There are a few ways in which you can become infected with an HPIV. An HPIV can survive on a hard surface for up to 10 hours. If you touch a contaminated surface with your hands and then touch your nose or mouth, you can become infected. The viruses can also infect you through droplet or close contact with someone who is already infected.

What Are the Symptoms of Parainfluenza?

Common symptoms of the four types of HPIV are very similar to those of the common cold. They include:

  • fever
  • cough
  • runny nose
  • stuffy nose
  • chest pain
  • sore throat
  • shortness of breath
  • wheezing
  • general difficulty breathing

Most often, the symptoms of parainfluenza viruses are not severe enough to cause concern in healthy adults. They can, however, be life-threatening in an infant, the elderly, or anyone else with a compromised or weakened immune system. Any such person with HPIV symptoms should see a doctor or go to the emergency room.

How Are HPIVs Diagnosed?

In most cases, your doctor will not bother to diagnose you as having a particular HPIV. Because healthy adults can recover normally without any treatment, there is no need for an exact diagnosis. If, however, you have a compromised immune system, your doctor may want to confirm that you have a particular HPIV.

Your doctor may simply do a physical exam to determine if your symptoms match those of HPIVs. For a more accurate diagnosis, a doctor may take a throat or nose swab to detect the presence of a virus and to identify it in a cell culture. Your doctor can also diagnose a specific virus by detecting antigens that your body has made to fight the virus.

To ascertain the extent of symptoms of HPIVs and to determine whether or not you have complications such as pneumonia, your doctor may order a chest X-ray or a CT scan of your chest. These are both imaging techniques that allow your doctor to see what is happening in your respiratory system.

Treatment of Parainfluenza

There is no treatment that can eliminate the HPIV from the body. When infected with HPIV, you just have to let it run its course.

Symptoms, however, can be treated with over-the-counter medications like saline nose drops and analgesics like aspirin or acetaminophen. Do not give aspirin to a child or teenager who has a fever and a viral infection. When given as treatment for a viral illness, aspirin has been associated with Reye’s syndrome, a serious and potentially deadly disorder.

Prevention of Parainfluenza

There are measures that you can take to prevent being infected with an HPIV. These include washing your hands regularly and disinfecting surfaces that can harbor the viruses. Avoiding close contact with those who are infected can also reduce your risk of becoming infected. There is currently no vaccine used to prevent HPIVs.

What Is the Long-Term Outlook for Parainfluenza?

In most people, an HPIV is not a serious illness. The symptoms can be very uncomfortable for several days, but as long as your immune system is functioning properly, you should be able to fight off the infection.

Infants, very young children, the elderly, and anyone with a weakened immune system are at risk from an HPIV infection. With medical treatment, however, even these individuals may recover.

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