There are four types of human parainfluenza viruses (HPIVs), which all cause respiratory infections. Most people get better without treatment, but the viruses can sometimes cause severe illness.

Parainfluenza refers to a group of viruses called human parainfluenza viruses (HPIVs). There are four viruses in this group. Each one causes different symptoms and illnesses.

All forms of HPIV cause an infection in either the upper or lower respiratory area of a person’s body.

Symptoms of HPIVs are often similar to those of the common cold. When cases are mild, the viruses may be misdiagnosed.

Most people who contract HPIV recover with no treatment. However, someone with a weakened immune system has a higher risk of developing a life threatening infection or complications.

Four types of HPIV exist. They all cause a respiratory infection, but the type of infection, symptoms, and location of the infection depends on the type of virus you have.

The four types of HPIV can occur in anyone.


HPIV-1 is a common cause of croup in children. Croup is a respiratory illness that appears as swelling near the vocal cords and in other parts of the upper respiratory system.

HPIV-1 is generally responsible for outbreaks of croup in the fall. In the United States, the outbreaks tend to be more widespread in odd-numbered years.


HPIV-2 causes croup in children, but doctors detect it much less often than HPIV-1. It’s seen mostly in the fall months but to a lesser degree than HPIV-1.


HPIV-3 is mostly associated with pneumonia and bronchiolitis, which is swelling from inflammation in the smallest airways in the lungs. It often causes infections in the spring and early summer, but it appears throughout the year.

With HPIV-3, the exact period of time you’re contagious hasn’t been determined. However, it has been shown that viral shedding — and therefore the risk of passing on HPIV-3 — may occur for several months even if you no longer have symptoms.


HPIV-4 is rarer than the other parainfluenza types. Unlike the other strains of HPIV, there are no known seasonal patterns of HPIV-4.

You may contract HPIV in several ways.

HPIV can survive on a porous surface for up to 10 hours. If you touch a contaminated surface with your hands and then touch your nose or mouth, you may contract the virus.

The viruses can also be transmitted by having close contact with someone who has HPIV. Contact includes touching them or being in an area (especially indoors) where they have been coughing or sneezing.

It usually takes between 2 and 7 days after transmission for symptoms to appear. Even if you’ve had HPIV before, it’s possible to contract it again.

HPIV-1 and HPIV-2 generally cause croup and symptoms similar to the common cold, while HPIV-3 and HPIV-4 often cause pneumonia and bronchiolitis.

Symptoms may include:

Most often, the symptoms of HPIVs are not severe enough to cause concern in healthy adults. But they can be life threatening in an infant, older adult, or anyone with a compromised or weakened immune system.

If you’re considered part of the high risk group and you develop HPIV symptoms, reach out to a doctor right away or go to an emergency room if symptoms worsen.

Your doctor may do a physical exam to determine if your symptoms match those of HPIVs.

For a more accurate diagnosis, a healthcare professional may take a throat or nasal swab. These can detect and identify the presence of a virus in cell cultures. Your doctor can also use them to detect antigens your body made to fight the virus.

Your doctor may order imaging tests, such as a chest X-ray or CT scan of your chest, to see what’s happening in your respiratory system. X-rays and CT scans can help your doctor determine the extent of your symptoms and whether you have complications such as pneumonia.

There’s no treatment that can eliminate an HPIV from your body. If you have contracted HPIV, you have to let it run its course, though you can do things to help ease symptoms.

Your doctor may prescribe corticosteroids to treat croup caused by an HPIV.

You can ease HPIV symptoms with over-the-counter medications and home treatments, including:

  • taking analgesics like aspirin (Bufferin) or acetaminophen (Tylenol)
  • using a humidifier
  • taking a hot shower

It’s important to note that children and teenagers who have a fever and viral infection should not take aspirin. Aspirin use in these age groups is linked to Reye’s syndrome, a life threatening condition.

You can take steps to prevent HPIV and other viral infections. These include:

  • washing your hands regularly
  • disinfecting surfaces that can harbor viruses
  • trying not to touch your eyes, mouth, or nose

Avoiding close contact with anyone who may have a viral infection can also lower your risk of developing an illness. If you’re sick, stay home if you can to prevent transmitting it to others.

There’s currently no vaccine that prevents HPIV.

An HPIV isn’t a serious illness for most people, but the symptoms can be very uncomfortable for several days. As long as your immune system is functioning properly, you will likely be able to clear the infection.

Anyone can get an HPIV, and healthy people will usually recover without treatment. However, the viruses can lead to serious illness in children, older adults, and people with compromised immune systems.

Anyone with symptoms of HPIV or other viral infections should stay home to avoid transmitting the virus to others. If you have severe symptoms or are part of a higher risk group, it’s important to reach out to a doctor.