Overview

Did you know that seasonal parainfluenza virus infection accounts for 40% of hospital admissions of children for lower respiratory tract-related illnesses?¹

What is parainfluenza?

Parainfluenza (also known as human parainfluenza virus or abbreviated HPIV) are viruses which causes respiratory infection by infecting cells in the upper airway (consisting of the nose, throat and voice box) and lower respiratory tract (the breathing windpipe, respiratory tree and lungs. 

There are four types of Parainfluenza from which type 1 is the most common to cause pathology in individuals.^1,2,3

Can parainfluenza be transmitted through contaminated surfaces (fomites)?

Parainfluenza can be transmitted via indirect contact with a surface through;

• Touching surfaces contaminated with parainfluenza virus particles such as door handles, computer keyboards , screens, taps, phones and subsequently touching the face (particularly nose, mouth and eyes)
• Viral particles can be suspended on surfaces. These resuspended viral particles on surfaces such as inside the home can contaminate the air and facilitate parainfluenza transmission from person to person via emission and inhalation of virus particles by an individual^4,5

Why is this question important?

The question investigating whether parainfluenza on contaminated surfaces is a transmission route is important for:

•  Determining the effectiveness of type and optimal concentration of disinfectant on contaminated surfaces
• Optimising common infection prevention practices such as covering the mouth and nose with a tissue whilst coughing and sneezing, binning used disposable materials such as tissues after use and washing hands regularly / or using antibacterial gel to prevent parainfluenza transmission between individuals

Parainfluenza virus types, symptoms and transmission passages

Types and Characteristics of human parainfluenza viruses 

There are four types of Parainfluenza: HPIV-1, HPIV- 2, HPIV-3, and HPIV-. These viruses are characterised into types by the diversity of their surface molecules (antigens) which trigger the immune response against the virus as well as their genetic makeup. It is worth mentioning that infections with HPIV-1- HPIV-3 commonly lead to lower respiratory tract infections.

Symptoms of parainfluenza virus

• Cold symptoms (which include an itchy and runny nose, coughing and sneezing frequently, sore throat and high temperature)
• Croup (a harsh, hoarse sounding cough) 
• Common chest infection (bronchiolitis)
• Pneumonia (a lung condition)¹

Demographics in which parainfluenza infection occurs

• Children under five years old and older adults are commonly affected by upper and lower respiratory tract infections caused by parainfluenza viruses
• Individuals with a weakened immune system (such as patients undergoing cancer chemotherapy and organ transplants, patients with HIV infection, or patients with chronic illnesses such as asthma and type 1 diabetes)⁶

Methods of parainfluenza transmission

Direct contact

• Parainfluenza virus can spread from person-to-person via direct physical contact such as touch and direct contact with objects and surfaces contaminated with viral particles spread by infected individuals⁴

 Indirect contact

• By airborne aerosol and droplet transmission through inhalation of viral particles by individuals which can be over short or long range distance
• Touching with contaminated surfaces and objects and by disturbing (for e.g. by walking on or touching) suspended viral particles on surfaces causing their release into the air
• Touching eyes, mouth and nose after touching a contaminated surface⁴

Studies on parainfluenza surface transmission

Survival of parainfluenza on various surfaces

The medium or materials of the contaminated objects or surfaces can affect parainfluenza virus transmission.

• A study of three strains of parainfluenza placed on different surface materials (non-absorptive materials which include stainless steel, laminated plastic and skin) and absorptive materials (hospital gown, facial tissue and laboratory coat) showed the virus remained the most prolonged period of time on stainless steel. The persistence of the virus remained up to 10 hours on non-absorptive surfaces and up to 4 hours on absorptive surfaces
• A similar study found that when HPIV is kept at room temperature on glass, plastics, metals and varnished wood (non-porous surfaces) it can survive from 2 hours to 1 week depending on environmental conditions
• Another study found HPIV can be transferred from stainless steel to fingers and remained living (viable) greater than 1 hour on the hands^7,2

Environmental conditions influencing viral persistence 

HPIV spread is influenced by environmental conditions such as temperature and humidity.²

• The resistance and stability of HPIV in the environment is the most at lower temperatures (4°C) and at normal pH levels (between pH 7.4–8.0), and survival of HPIV viral particles decreases notably at higher temperatures (37°C) and low humidity (less moisture in the air)
• At room temperature (between 18-22°C), HPIV on nonporous materials (such as glass, plastics, metals, and varnished wood) survives from a timeframe between 2 hours to 1 week depending on environmental conditions. The mean survival of HPIV on porous surfaces (such as sponges, wood and rubber) is approximately 4 hours²

Epidemiological studies on parainfluenza

Case studies

It has been shown that frequency of use and continual exposure to a surface determines the surface transmission of the parainfluenza virus.²

A study looking at office settings in Arizona found most HPIV-positive surfaces were offices in the athletic department, which had a high influx of people and workspace being shared with more than two people. Furthermore, several workers were concurrently ill in the course of the study sampling period.²

Insights from influenza and coronavirus research

Research on coronaviruses shows certain materials of surfaces such as plastic promote longer viral survival (between 8 hours to 28 days) than stainless steel (between 8 hours to 5 days), with copper surfaces (between 20 minutes to 8 hours) showing the lowest viral particle survival (between 20 minutes to 8 hours) comparative to the former two.⁸ These findings are similar to studies on parainfluenza fomite transmission.

Another article showed that 4.2% of influenza A infection risk comes from contaminated surfaces. In a study set in a graduate office setting, it was shown that 95.1% of viral transmission was through private surfaces (the desk) and 4.9% through public surfaces.⁹

Implications for parainfluenza

Implications include knowing how to mitigate fomite transmission of parainfluenza, through a variety of techniques;

• Hand washing regularly and using sanitiser
• Cleaning surfaces with disinfectants regularly 
• Opening windows and doors to improve ventilation and prevent aerosolized and droplet-mediated viral transmission 
• Removing old bedsheets and linen and washing them at high temperatures with disinfectant containing washing products 
• Do not touch your eyes, nose and mouth as virus particles cause infection by entering these areas.

Preventing fomite virus transmission

Using disinfectants against parainfluenza

Chloride and peroxide-based disinfectants degrade the genetic material of the parainfluenza virus thus preventing its transmission to humans and its replication inside the human body to cause infection.²

Detergents and sanitisers such as soaps and washing-up liquid have been shown to promote cross-contamination to clean surfaces and are ineffective in eliminating viral contamination on surfaces.²

Frequency and methods of cleaning surfaces

The frequency of cleaning should be regular, particularly if you are in close contact with someone who has a parainfluenza infection. 

Furthermore, product information on labels should be checked before usage to ensure optimal results and safety for the consumer.

The steps of cleaning (reducing germs by using detergent/soap), disinfecting (using a chloride/peroxide/alcohol-based disinfectant according to prescribed guidelines on the chosen product) and sanitisation of surfaces will reduce chances of parainfluenza transmission.

Steps for maintaining hand hygiene

• Ensure contaminated surfaces are cleaned, disinfected and sanitised 
• Rinse hands with water thoroughly
• Use a hand wash/soap to clean palms of hands, back of hands, back of fingers, front of fingers, in between fingers and with a rubbing motion of the two hands nails together for 15-20 seconds
• Rinse hands making sure all soap is removed
• Wipe hands with a fresh and clean towel¹⁰

Future studies

Further research could focus on; 

• Investigating how surface transmission causes parainfluenza by touch and resuspension into the air by walking or opening a door for instance
• Determining the infectivity and transmission ability of the fomite surfaces which release viral particles
• Examining the minimum and maximum infectious dose of parainfluenza particles required from fomite transmission to cause infection
• Further studies on how parainfluenza can survive on certain surface materials for longer periods than others
• Measuring how hand washing can reduce contaminated surface transmission of parainfluenza

FAQ’s

How is the parainfluenza virus transmitted?

Parainfluenza can be transmitted through a direct route (by contact with a person by touch) and an indirect route (contaminated surface transmission of parainfluenza by touching the surface and subsequently the face or via inhalation of aerosol and droplet viral particles).

How can you prevent the spread of parainfluenza?

By washing hands and using hand sanitiser, washing linen, clothes and bedsheets of infected individuals after the infection period, covering the mouth with a tissue whilst coughing, cleaning, disinfecting and sanitising surfaces and not touching eyes, nose and mouth can prevent parainfluenza spread.

Summary

Parainfluenza viruses can remain on surfaces for hours to days, depending on the moisture in the air and the temperature which influences their stability.

Lower temperatures and medium levels of humidity favour parainfluenza virus survival whereas higher temperatures and lower humidity lessens parainfluenza survival time. 

Non-absorptive surfaces promote longer parainfluenza survival time as compared to absorptive surfaces. Fomites can transmit parainfluenza by a person touching the fomite and touching their nose, eyes or mouth. Maintaining hand hygiene and using disinfectants can kill viral particles on surfaces.