Introduction

Human parainfluenza refers to a group of viruses that lead to the development of respiratory infections. Parainfluenza infections are most common in children and infants, and most children will have a parainfluenza virus infection by 5 years old. There are currently no licensed antiviral medications for parainfluenza, however, treatments are being developed to treat more severe cases.¹

Understanding parainfluenza

Human parainfluenza viruses belong to the same group of viruses that cause mumps and measles. These viruses cause upper and lower respiratory tract illnesses. Despite causing mild infections in healthy individuals, parainfluenza viruses can cause severe infections in immunocompromised individuals.² This highlights the need for effective antiviral treatments.

Parainfluenza viruses are grouped into 4 types, HPIV-1, HPIV-2, HPIV-3, and HPIV-4. HPIV-1 and HPIV-3 are the types that cause the most lower respiratory infections.

Infections are mostly common in children and are one of the main causes of hospitalisation in infants and children under 5. Infections can present as a common cold, ear infection, croup, or viral pneumonia. Symptoms depend on the type of respiratory illness.

Croup: a condition seen in childhood that affects the windpipe, the voice box, and the lung airways. It presents in children with a fever, a hoarse barking cough, and sometimes wheezing. It can also be seen on a radiograph.

Bronchiolitis: a chest infection, which affects children under 2 years of age.  It presents as a fever and nasal congestion, spreads to the lower respiratory tract and leads to symptoms such as coughing and rales. Children usually recover in 21 days.

Pneumonia: inflammation in the lungs caused by an infection that occurs in people of all ages. It can be serious in babies, older people, and people with heart and lung conditions.  It presents as a fever, cough, or diarrhoea in children.

Tracheobronchitis: inflammation of the lower and large airways that isn’t croup, bronchiolitis or pneumonia. It presents as a cough with a fever and an upper respiratory tract infection.

Human parainfluenza is airborne and is spread through sneezing or touching an infected surface. Infections can exacerbate chronic obstructive pulmonary disease (COPD) and asthma.

Complications of parainfluenza infections

Complications of parainfluenza infections can occur in immunocompromised patients and the elderly. Infections caused by HPIV-3 usually cause more serious illness in immunocompromised people and HPIV-4 rarely causes severe illness.

 The illness may lead to the use of mechanical ventilation and lead to death. Infection with parainfluenza in children can lead to the development of asthma and COPD later on in life. Early diagnosis and the treatment of symptoms are very important, especially in immunocompromised patients.

Role of antiviral medications

Antiviral medications are a class of drugs that are used to treat viral infections.³ Drugs are available to treat influenza A, such as amantadine to inhibit viral replication.⁴ Early treatment with antiviral drugs can prevent the exacerbation of chronic respiratory viral infections. However, there is currently no antiviral treatment that is effective against parainfluenza viruses. There is current research investigating the development of antiviral treatments against parainfluenza infections, where the virus is prevented from entering the cell causing an infection.² However, further research is required before a drug can be developed, tested, and approved for use.

Clinical management of parainfluenza

There is no specific antiviral drug used to treat human parainfluenza infections. However, illness caused by the virus is usually mild, and treatment focuses on relieving symptoms. The Centers for Disease Control and Prevention (CDC) recommends those sick with parainfluenza:

• Take over-the-counter fever and pain medication (ibuprofen)
• Drinks liquids
• Rest at home

To note: antibiotics are only effective against bacterial infections, not viral infections such as parainfluenza. Therefore, your doctor will not prescribe antibiotics for the treatment of parainfluenza infections.

Certain infections caused by the parainfluenza virus have specific treatments. Corticosteroids are effective for mild, moderate, and severe croup.

Prevention of parainfluenza

There is currently no vaccine against parainfluenza infections, although there are ways to reduce your risk of catching it.

Methods to reduce the risk of catching and spreading parainfluenza include:

• Washing hands with soap
• Avoid coughing into the air
• Avoid touching eyes, mouth, and nose with dirty hands
• Avoid close contact with people sick with parainfluenza
• Stay home if sick with parainfluenza
• Wear a mask if outside for necessary purposes

During a human parainfluenza outbreak, immunocompromised people should practice physical distancing and wearing masks to reduce the risk of contracting the virus.

Conclusion

Parainfluenza viruses lead to respiratory infections, most commonly in children. Unfortunately, there is no antiviral medication available to treat parainfluenza, however, there are over-the-counter medications available to elevate symptoms. Early diagnosis is imperative in immunocompromised people and the elderly. Researchers are working on the development of antiviral medication to treat parainfluenza infections.

FAQs

Can parainfluenza infection lead to complications in healthy people?

Most parainfluenza infections are mild; however, they can rarely lead to complications in healthy people, namely causing asthma.

Can pets transmit human parainfluenza infections to humans?

There is currently no evidence to suggest that animals transmit human parainfluenza.

Where can I find more information about current research in antiviral treatments?

The latest research and clinical trials can be accessed from medical journals. Government health agencies also report on newly approved medication.