Parainfluenza viruses are a group of four types of viruses. They are a common cause of respiratory (breathing) illnesses. These illnesses can affect your, nose, throat, lungs, and bronchial tubes (the airways that carry air to your lungs). Parainfluenza tests check whether a parainfluenza virus is causing an illness. The tests usually use a sample of fluid from your nose or mucus from your lungs.

Parainfluenza viruses are also called human parainfluenza viruses (HPIVs). They aren't the same as flu (influenza) viruses. The flu is more common in winter. In the U.S., parainfluenza viruses are more common in the spring, summer, and fall.

Like the flu, parainfluenza spreads easily from person to person. It can spread through the air when a person with the infection coughs or sneezes. You can also get the flu by touching a surface that has the flu virus on it, and then touching your mouth, nose, or eyes.

Parainfluenza viruses commonly cause respiratory illness in babies and younger children, but anyone can get sick from these viruses. You can also have parainfluenza illnesses many times in your life. If you're healthy, you'll probably have mild symptoms that are much like a common cold, such a runny nose, fever, or cough. And you'll usually get better on your own.

Older adults and people of all ages who have weakened immune systems are more likely to develop more serious illness from parainfluenza infections. These illnesses include croup, bronchitis, and pneumonia.

The most common test for parainfluenza viruses is a molecular test, such as a PCR (polymerase chain reaction) tests. These tests can find very small amounts of genetic material from parainfluenza viruses in the fluid sample from your nose or lungs.

Other tests for parainfluenza virus are used less often than molecular tests. Rapid antigen tests are less accurate and must be done within a week after symptoms begin. Viral culture tests take much longer than other tests. And blood tests are mainly used for research.

Most healthy people who have symptoms of a respiratory illness do not need parainfluenza testing. That's because they usually get better on their own. But you may need this test if you have a high risk of getting seriously ill from a parainfluenza infection because you:

• Have a condition that affects your immune system, such as:
  • Blood stem cell or bone marrow transplants
  • Organ transplantation
  • Blood cancers
  • HIV
• Have a heart or lung disorder
• Are in the hospital with community-acquired pneumonia (pneumonia that you catch during your usual daily life, not from spending time in a hospital or other health facility)
• Are an older adult

For these people, treatment decisions depend on knowing whether they have a viral or bacterial infection. So, parainfluenza testing may be done as part of a respiratory pathogens panel. This is a group of tests that checks for several viruses and bacteria that cause respiratory illnesses. There is no cure for parainfluenza viruses, but bacterial infections may be treated with antibiotics.

You or your child may need a parainfluenza test if either of you have:

• Symptoms of a respiratory illness.
• And another condition that increases your risk of getting seriously sick from a parainfluenza illness.

Symptoms of parainfluenza and other respiratory illnesses may include:

• Fever
• Sore throat
• Wheezing
• A long-lasting cough that may sound like a barking in children (croup)
• Shortness of breath
• Too much mucus in the lungs or airways (congestion)
• Rapid breathing

Tests to diagnose parainfluenza viruses are usually done on a sample of fluid from your nose or chest.

A sample from your nose may be used if you've had symptoms between 3 and 7 days. Most tests are done with this type of sample. The sample may be collected using one of these methods:

• Nasal aspirate or wash. To do a nasal aspirate, a health care professional will insert a saline solution (salt water) into your nose and remove it with gentle suction.
• Swab test. A health care professional will use a special swab to take a sample from either:
  • Deep in the back of your nose
  • An inch deep inside both of your nostrils and from your throat using a separate swab inserted through your mouth

A sample from your chest may be used at any time during your illness. The fluid may be collected with one of these methods:

• Sputum test. Sputum is a thick mucus from the lungs. It is different from saliva (spit). To get a sample, you will be asked to cough up sputum into a special container.
• Bronchoalveolar lavage (BAL). A BAL collects a sample of fluid from your lung. This type of sample is usually used only if you are very ill. A doctor will insert a narrow, flexible tube (a bronchoscope) down your throat and into your lung. A small amount of salt water will be injected through the tube into your lung and then suctioned out. Numbing medicine will be used in your mouth and throat. You may also have medicine to help you relax.

If you have a BAL, you may need to fast (not eat or drink) for several hours before the test. You should plan to have someone take you home because you may feel sleepy if you are given medicine to relax.

You don't need any special preparations for other parainfluenza tests.

There is very little risk to having a parainfluenza test:

• A nasal aspirate or wash may feel uncomfortable. These effects are temporary.
• Nasal and throat swabs may cause a brief gagging feeling.
• A BAL may cause a sore throat for a few days. Serious problems are rare. They include bleeding in the airways, infection, or a partly collapsed lung.

A negative result means that no signs of parainfluenza viruses were found in your sample. Another illness is probably causing your symptoms. But a negative test result doesn't rule out a parainfluenza illness. It's possible that there was too little virus in your sample for the test to find.

A positive result means that you likely have a parainfluenza infection. But it's possible for a PCR test to show signs of a virus even though you don't have enough virus in your body to make you sick.

Talk with your provider about what your test results mean.