A Complete Overview of Parainfluenza

Human parainfluenza viruses (HPIV) can infect the respiratory system and cause cold-like symptoms. HPIV‘s respiratory symptoms are typically mild but can cause bronchitis, croup, or pneumonia. HPIV, or parainfluenza, is part of a family of viruses known as Paramyxoviridae, which can cause upper and lower respiratory tract infections. They differ from the influenza virus.

Children, people with impaired immune systems, and older people most commonly contract these viruses. However, anyone can acquire HPIV.

This article discusses the types, causes, and symptoms of parainfluenza, treatment, and outlook. It also explains the differences between other respiratory infections and answers some frequently asked questions.

There are four types of parainfluenza and two subtypes of the fourth. The types vary based on the infection, symptoms, and location of the infection they cause.

Parainfluenza outbreaks tend to occur at specific times of the year. Still, it is possible to contract HPIV infections at any time of the year.

Clinicians may also refer to this as HPIV-1.

Parainfluenza 1 and 2 commonly cause croup, an upper respiratory infection that can impair breathing and cause a hoarse, barking cough.

Cases of parainfluenza 1 tend to increase every other year, usually in odd-numbered years from September to December.

It can also cause lower respiratory infections.

Like parainfluenza 1, parainfluenza 2 (HPIV-2) may also cause croup or cold-like symptoms or lower respiratory tract infection.

The condition also occurs every other year, usually in even-numbered years. Also, parainfluenza 2 may occur less frequently than parainfluenza 1.

Outbreaks of parainfluenza 3, or HPIV-3, tend to occur annually between April and June. However, in some years, when HPIV-1 is not circulating, HPIV-3 typically has a longer season that may extend into the fall. 

HPIV-3 may cause illnesses such as: 

• Bronchiolitis: This infection of the airways affects children ages 2 or under. Symptoms include fever and nasal congestion and sometimes difficulty breathing or eating.
• Bronchitis: Bronchitis refers to inflammation of the lungs’ airways. It can cause a cough, chest pain, fatigue, or a sore throat. 
• Pneumonia: This lung infection is one of the leading causes of hospitalization among adults in the United States. It can cause fever, cough, and shortness of breath.

Parainfluenza 3 sometimes causes more severe illness in people with compromised immune systems than other types of parainfluenza.

Parainfluenza 4, or HPIV-4, has two subtypes: HPIV-4A and HPIV-4B.

Clinicians rarely associate parainfluenza 4 types with severe illness, although it can occur. Clinicians also see it less than other types of parainfluenza.

Though HPIV-4 may be less seasonal than other types, the virus occasionally follows the outbreak pattern of HPIV-3.

Parainfluenza can cause mild to serious illnesses.

Viral parainfluenza symptoms include upper and lower respiratory signs, such as:

• nasal congestion
• headache
• sore throat
• fatigue
• general feeling of being unwell
• cough with or without mucus
• chest pain
• fever

Symptoms may develop 2–7 days after exposure to the virus, although this period can vary.

Parainfluenza and influenza, or flu, are different despite having a similar name.

The conditions share some similarities: They are both respiratory infections and can cause similar symptoms. Also, they can spread the same way.

However, parainfluenza and influenza result from two kinds of viruses. While parainfluenza results from infection with Paramyxoviridae, influenza is due to infection with the family of viruses known as Orthomyxoviridae.

Vaccines and antiviral medications are available for influenza, but they are not available for HPIV.

Like parainfluenza, COVID-19 is a viral infection. Both viruses can cause respiratory symptoms and can be spread via airborne droplets.

However, COVID-19 is caused by a virus known as SARS-CoV-2. COVID-19 can also cause different symptoms, such as loss of taste or smell and diarrhea. 

Also, vaccines are available for COVID-19 but not available for parainfluenza. 

HPIV is usually spread via direct contact with a person with the condition. People with HPIV can transmit the virus through airborne droplets from breathing, coughing, or sneezing. Also, others can acquire the virus by touching surfaces with droplets. 

The virus remains infectious in airborne droplets for over an hour and several hours when on a surface, depending on the environment. 

It is possible to acquire HPIV infections several times. The illnesses cause mild cold-like symptoms. However, reinfections can cause severe illnesses such as bronchitis or pneumonia. People with compromised immune systems and older people are more at risk for reinfection. 

Measures to avoid acquiring or transmitting a parainfluenza virus include:

• washing your hands often by using soap and water for at least 20 seconds
• avoiding close contact with people who have symptoms
• avoiding touching your face, mouth, eyes, or nose
• disinfecting objects and surfaces a sick person may have touched
• staying at home and away from others if you are sick, if possible
• covering your mouth and nose when you sneeze or cough
• washing your hands after coughing, sneezing, or blowing your nose

A doctor will ask about your symptoms and medical history and conduct a physical assessment. They may check for fever, listen to your lungs, and look at the back of your throat.

To be certain about a cause, clinicians may order lab tests. Parainfluenza illnesses may appear as other conditions. However, in mild cases, diagnostic testing may not be necessary.

Depending on the severity of the symptoms, medical professionals may also want to take a sample for laboratory testing to identify the cause of infection. 

Several methods are available for taking samples, including:

• nasal swab
• throat swab
• sputum sample

Many parainfluenza cases resolve on their own. There are no medications for parainfluenza viruses. Treatment centers on alleviating the symptoms.

For croup or pneumonia, your doctor may prescribe:

• corticosteroids such as dexamethasone
• epinephrine taken through a nebulizer
• oxygen therapy
• bronchodilator medication such as albuterol

At-home or self-management techniques may help to alleviate mild to moderate symptoms. These can include:

• getting lots of rest
• staying hydrated with water, broth, or tea
• using a humidifier or taking a hot shower
• taking over-the-counter (OTC) medications for cough or cold
• taking OTC pain relief medication or nonsteroidal anti-inflammatory drugs

Always check with a doctor or pharmacist before giving any OTC medications to children.

Read more about treatments for mild respiratory infections.

Parainfluenza can range from mild to serious illness.

Young children, older people, and people with weakened immune systems are at higher risk for developing serious illnesses such as pneumonia or bronchitis from HPIV. 

In some people, this can lead to hospitalization or death.

Also, having HPIV or another virus from Paramyxoviridae in early childhood may result in asthma and chronic obstructive pulmonary disease (COPD) later in life.

However, early medical attention and treatment can improve the outlook of the condition.

Seek medical attention for severe or recurrent symptoms of parainfluenza.

HPIV, or parainfluenza, is a viral respiratory infection. It can cause upper and lower respiratory symptoms such as runny nose and cough. More severe cases may develop into pneumonia, croup, or bronchitis. 

Most of the time, HPIV does not require medical treatment. Instead, treatment aims to alleviate the symptoms. However, people with weakened immune systems, children, and older people may be at risk for serious illness or complications. Early medical care can help to improve the outlook.

Seek emergency medical care for any difficulty breathing.