Overview

Human parainfluenza viruses (HPIVs) are single-stranded RNA viruses belonging to the paramyxoviridae family causing upper and lower respiratory tract infections. HPIV is divided into four serotypes- HPIV-1, HPIV-2, HPIV-3 and HPIV-4.² Two subtypes circulate at different times of the year. The primary routes of transmission involve direct person-to-person contact and respiratory droplets. These pathogens can affect anyone therefore, read on to understand the routes of transmission, the factors influencing transmission and preventative strategies.

Transmission routes

Parainfluenza viruses can spread through various transmission routes. Respiratory viruses are transmitted between individuals when the virus is released from the respiratory tract of an infected person and is subsequently transferred through the environment. Thus, leading to an exposed and susceptible person being infected.

Figure 1. Modes of transmission during short-range and long-range transmission.¹

Direct contact transmission

Direct contact involves the transfer of the virus from an infected individual to a susceptible host via physical contact or close proximity. This occurs through respiratory droplets during coughing or sneezing, facilitating direct transmission of the virus to the respiratory tract's mucous membranes at short range seen in Figure 1.

Indirect contact transmission

Indirect contact transmission occurs when the virus is transferred through contaminated intermediate objects, allowing transmission to susceptible individuals upon contact with contaminated surfaces (fomite).¹ HPIV may remain on surfaces for a few hours.

Airborne transmission

Airborne transmission occurs when infectious particles suspended in the air can travel longer distances (seen in Figure 1), potentially leading to inhalation and infection of vulnerable individuals. HPIV may remain infectious in airborne droplets for over an hour.

Factors influencing transmission 

HPIV is affected by environmental conditions playing a pivotal role in its survival. Environmental conditions include temperature, humidity and pH.⁴ Environmental conditions can affect the stability of parainfluenza viruses both on surfaces and in the air. This stability varies depending on factors like temperature, humidity, and surface type. In addition, host factors also play a role in the spread of the virus. Variables such as immune status and age can influence an individual's susceptibility to infection and their ability to transmit the virus. People with weakened immune systems or younger individuals may be more susceptible to contracting and spreading parainfluenza viruses. Understanding these factors is crucial for implementing effective prevention strategies and controlling the spread of infections caused by parainfluenza viruses.

Prevention strategies

Currently, there is no vaccine for the prevention and protection against parainfluenza infection.² However, these strategies will help reduce the risk of HPIV transmission:

• Maintain proper hand hygiene: Wash hands with soap for at least 20 seconds. Hand hygiene should be practised regularly, before eating, after coughing and after contact with potentially contaminated surfaces. Additionally, try not to touch your eyes, mouth or nose
• Environmental: Disinfect frequently touched surfaces and objects to remove the potential harbouring of the virus
• Respiratory hygiene: Cover yourself when coughing and sneezing with a tissue or the elbow to prevent the spread and transmission of respiratory droplets
• Avoid crowded settings: Minimise close contact with individuals who may be asymptomatic, particularly during periods of high respiratory virus activity

Implementing these strategies will help to reduce the transmission of parainfluenza viruses protecting susceptible individuals and public health.

Summary

HPIV viruses can spread through various modes of transmission; therefore, it is essential to reduce the risks of transmission against vulnerable individuals and protect yourselves and others against parainfluenza virus infections.

FAQs

What are the symptoms of parainfluenza infection?

Symptoms vary depending on the type of parainfluenza virus infection. Common symptoms of illnesses caused by HPIVs include cough, croup, rhinorrhea, bronchitis and pneumonia. HPIV-1 and HPIV-2 cause croup mainly in children whereas HPIV-3 and HPIV-4 cause pneumonia and bronchiolitis with HPIV-3 resulting in more hospitalisations.³

Who is at risk of parainfluenza infection?

Anyone can be infected with parainfluenza viruses however, infants, young children and the elderly are at higher risk of developing severe complications from parainfluenza virus infections.

What should I do if I think I have been exposed to parainfluenza?

If you believe you have been exposed to parainfluenza or are experiencing symptoms, contact your healthcare provider for further guidance and evaluation.

Are there any treatments for the parainfluenza virus?

Currently, there are no antiviral agents for parainfluenza virus infection.³ However, there are common approaches to help alleviate symptoms:

• Your doctor may prescribe corticosteroids in the form of dexamethasone or prednisolone.²
• Taking over-the-counter medications such as acetaminophen or ibuprofen to reduce fever and relieve pain.
• Using a humidifier to reduce airway inflammation
• Encouraging fluids and rest