What is parainfluenza?

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 like those of the common cold. When cases are mild, the viruses are often misdiagnosed. Most healthy people infected with an HPIV recover with no treatment. However, a person with a weakened immune system is at risk for developing a life-threatening infection.

Four types of HPIV exist. They all cause a respiratory infection, but the type of infection, symptoms, and location of the infection depend on the type of virus you have. The four types of HPIV can infect anyone.


HPIV-1 is the leading cause of croup in children. Croup is a respiratory illness that manifests as swelling near the vocal cords and in other parts of the upper respiratory system. HPIV-1 is responsible for outbreaks of croup in the autumn. 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 autumn but to a lesser degree than HPIV-1.


An HPIV-3 infection 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, typically occurs within the first 3 to 10 days of symptoms. In rare cases, viral shedding has been seen up to three to four weeks.


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

You can become infected by an HPIV in several ways. 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 close contact with an infected person. It usually takes between two and seven days after infection for symptoms to occur.

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
  • difficulty breathing

Most often, the symptoms of HPIVs aren’t 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 part of a high-risk group and you have HPIV symptoms, you should see a doctor or go to the emergency room.

If you aren’t part of a high-risk group, your doctor may not diagnose your strain of HPIV. If you have a compromised immune system, your doctor may want to confirm the particular type of HPIV.

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

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’s happening in your respiratory system. X-rays and CT scans can help your doctor determine the extent of symptoms and whether you have complications such as pneumonia.

There’s no treatment that can eliminate an HPIV from your body. If you have an HPIV infection, you just have to let it run its course.

Symptoms can be treated with over-the-counter medications like saline nose drops and analgesics like aspirin (Bufferin) or acetaminophen (Tylenol).

However, it’s important to note that children and teenagers who have a fever and a viral infection shouldn’t take aspirin. Aspirin is linked to Reye’s syndrome, a life-threatening disorder, when it’s used to treat a viral illness.

Cool mist humidifiers can help children with croup breathe better.

You can take steps to prevent infection with an HPIV. Wash your hands regularly and disinfect surfaces that can harbor viruses. Avoiding close contact with infected people can also lower your risk of becoming infected.

There’s currently no vaccine that prevents HPIV infection.

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 should be able to fight off the infection.