Introduction

Parainfluenza viruses are a group of infectious pathogens that cause a range of respiratory illnesses, from mild colds to severe conditions, such as pneumonia.¹ Understanding how long these viruses survive outside the body is crucial for preventing their spread, especially in hospitals and childcare facilities. Parainfluenza refers to a group of human parainfluenza viruses (HPIVs). These viruses are responsible for upper and lower respiratory illnesses, presenting symptoms such as sore throat, cough, and shortness of breath. While HPIVs can infect individuals of all ages, they are most common in infants and young children.² The viruses can infect a person multiple times throughout their life, though subsequent infections tend to be less severe due to partial immunity developed during earlier infections.

Parainfluenza infections are particularly prevalent during the autumn, winter, and spring months. It is important to understand how parainfluenza viruses survive outside the body, so we are able to identify, treat and prevent their spread.³

This article explores the nature of parainfluenza viruses, their modes of transmission, and their survival on various surfaces.

Types of parainfluenza virus (HPIV 1-4) 

There are 4 main types of parainfluenza viruses: ²

• HPIV-1 and HPIV-2: These types are commonly associated with croup and colds in young children
• HPIV-3: Often leads to more serious respiratory tract infections such as bronchiolitis and pneumonia
• HPIV-4: Less is known about this type, but it is thought to cause respiratory illnesses similar to HPIV-3

Knowledge of how long HPIVs can survive outside the body aids in understanding their transmission dynamics. This is vital for the development of guidelines and protocols to control outbreaks, particularly in settings like schools and hospitals where vulnerable populations are present.

Transmission of parainfluenza viruses

HPIVs are highly contagious and can spread through various routes:^4,5

• Direct contact: Physical interaction with an infected person
• Indirect contact: Touching surfaces contaminated with the virus and then touching the face, mouth, nose, or eyes
• Droplet transmission: Inhalation of respiratory droplets expelled when an infected person coughs or sneezes
• Aerosol transmission: inhalation of fine viral particles suspended in the air

Factors affecting survival of parainfluenza virus outside the body

There are many surfaces on which this virus can live, here are some examples: ⁴

• Hard non-porous surfaces: Parainfluenza viruses can remain viable for several hours on surfaces like door handles, light switches, and tabletops
• Soft, porous surfaces: On softer, more absorbent materials, such as towels and tissues, the viruses typically survive for shorter periods
• Hands and skin: The transient nature of HPIV on hands and skin, surviving only minutes to an hour, highlights the importance of regular and thorough handwashing

Environmental conditions also play a role in the survival of the parainfluenza virus, these include:

• Temperature: The virus tends to survive longer in cooler temperatures, which can facilitate the spread during colder months
• Humidity: High humidity levels have been shown to extend the viability of HPIVs outside the body
• Exposure to sunlight: Ultraviolet (UV) radiation from sunlight significantly reduces the survival time of these viruses, which can decrease the risk of transmission in outdoor settings

They also thrive in certain biological conditions. The presence of organic materials such as mucus or blood can protect the virus, enhancing its survival time on various surfaces

The survival of parainfluenza viruses on surfaces can vary based on the type of surface and environmental conditions.⁶

Implications for infection control

HPIVs can be spread through direct contact with infected individuals or through indirect contact by touching contaminated surfaces followed by touching the face. Given the ability of HPIVs to survive on surfaces for several hours, it is essential to adopt preventive measures to reduce the risk of infection:

1. Hand hygiene: Regular handwashing with soap and water for at least 20 seconds. If soap and water are unavailable, use an alcohol-based hand sanitiser
2. Avoid touching the face: Refraining from touching the eyes, nose, and mouth
3. Cleaning and disinfecting surfaces: Regularly cleaning high-touch surfaces such as doorknobs, light switches, and electronic devices
4. Using masks: Wearing masks in crowded places or when in close contact with infected individuals.
5. Isolation: Staying home and avoiding close contact with others when sick

Symptoms and management of parainfluenza

Symptoms of HPIVs can range from mild to severe and include:

• Fever
• Cough
• Runny or stuffy nose
• Sore throat
• Wheezing
• Hoarseness
• Sneezing 

Diagnosis and treatment

Diagnosis of parainfluenza is usually based on symptoms and a physical examination. In some cases, a healthcare provider may take a mucus sample from the nose or throat to test for the presence of HPIVs. There is no specific antiviral treatment for HPIV infections, and antibiotics are not effective as they target bacterial infections, not viral ones. Most people recover on their own with supportive care, including

• Rest
• Hydration
• Use of over-the-counter medications to alleviate fever and pain
• In severe cases, medical attention may be required, especially for young children, older adults, or individuals with compromised immune systems.

Complications and when to seek medical attention

Complications from HPIVs can include severe respiratory conditions like pneumonia and croup, which may require hospitalisation. It is important to seek medical attention if you or your child experiences severe symptoms such as a high fever (over 103°F or 40°C), difficulty breathing, chest pain, or signs of dehydration.

Summary

Understanding the survival of parainfluenza viruses (HPIVs) outside the body is essential for effective infection control and prevention, particularly in environments where vulnerable populations are present, such as hospitals and childcare facilities. HPIVs, responsible for a range of respiratory illnesses, can persist on various surfaces for different durations depending on environmental conditions and surface types.

Public awareness and adherence to recommended hygiene practices are crucial in controlling the spread of these viruses and protecting public health.