Do cold and flu viruses stay contagious outside of the body? - FluCamp

Now that the Christmas season is well and truly over, and the winter nights have set in, it can only mean one thing – the cold and flu season is in full effect.

As temperatures start to fall, the chances of catching a cold increase, and so does the risk of spreading it to your family or people around you. With the average person getting a cold two to three times per year, according to the Centers for Disease Control and Prevention, it can’t hurt to know how to prevent them as much as you can – including how long they can last outside of the body.

Tame that flu

Cold and flu viruses, despite their fearsome reputation, are actually structurally very weak. So, contrary to popular belief, and contrary to what the many commercials for cleaning products might suggest, these pathogens don’t actually last for weeks, or even days, outside the body. That’s because cold and flu viruses cannot bear the harsh conditions of the dry, outside world, even though they can be ferocious inside the body.

Here’s what you need to know about how long cold and flu viruses stick around for, and how you can protect yourself against them!

What is the cold? What is the flu?

Rhinovirus is the most common viral infectious agent in humans, with coronavirus, parainfluenza and respiratory syncytial virus also being sources. All can lead to serious complications like bronchitis and pneumonia, especially in individuals with respiratory conditions such as asthma, and in those with compromised immune systems, such as the very young and elderly.

Influenza A is the main family of viruses behind the flu in humans, with stats from the World Health Organisation (WHO) showing that the flu kills between 250,000 and 500,000 people around the world every year.

Individuals with cold or flu infections can spread contagious viruses before symptoms even begin to manifest. Viruses on their own cannot multiply, and must infect the cells of a living creature in order to reproduce. Confusion can be caused when the term living is used to describe viruses because, in fact, they aren’t actually living entities at all.

You may hear people say “a virus can live on a doorknob for four days” – but Drs at the National Institute of Allergy and Infectious Disease say that this isn’t the case. “Maybe you can isolate it and grow it in culture by swabbing a doorknob, but that doesn’t mean that it’s infectious for four days,” one explains.

This is usually what advertisements for cleaning products are referring to when they say flu viruses can survive on surfaces for days on end. An intact virus is necessary for an infection, but this propensity reduces over time as its structures begin to degrade. Once weakened, the virus is less able to attach to cells and spread its genetic material – meaning that it is no longer able to go on and infect further humans.


How long are cold and flu viruses infectious?

In the past 10 years alone, scientists have come leaps and bounds in understanding how long flu viruses retain their infectiousness on common surfaces. In a 1982 study, influenza was found to remain contagious for up to 48 hours on hard plastic or stainless steel, while a 2008 publication decided that these viruses stayed infectious for up to three days on banknotes.

Though in actuality, influenza viruses may actually have a much shorter infectious lifespan then suggested. This is backed by the recent work of virologists at Public Health England. In a 2011 study, a team took two strains of Influenza A and analysed how long they remain infectious on a variety of household surfaces. After only nine hours, viruses with the capability to infect people were no longer found on most non-porous metal and plastic surfaces, such as aluminium and computer keyboards. On more absorbent materials and fabrics, such as soft toys and wooden surfaces, viable viruses disappeared after only four hours.

Although this research is thorough, it is still hard to truly decide on a number – due to the vast array of viruses that can cause infections. In general, most are no longer dangerous after 24 hours, and their ability to infect dissipates faster on porous materials like facial tissues.

What’s the best surface for killing viruses?

In the cases of both flu and cold-causing viruses, infectious particles on our hands are usually gone after 20 minutes, meaning that our skin is one of the most protective surfaces.

Our body’s immune system acts a defensive barrier which does a great job at killing viruses. On top of that, our skin has its own bacteria living on it which doesn’t harbour viruses well – which is good news for us.


Why don’t cold and flu viruses live forever?

The rapid decrease in infectiousness with cold and flu viruses once they’re outside the body is down to three main factors: their structure, environmental conditions, and how much our mucus surrounds it after we sneeze.

Temperature, ultraviolet radiation from sunlight, pH changes and salt can play a role in weakening a virus, but one of the main factors is moisture. If pathogens live in warm, moist environments, like the body, they’re more stable – however, when exposed to a different environment, the structure can break down. This highlights why cold and flu viruses remain infectious on non-porous surfaces, like light switches and counters, longer than porous surfaces such as fabric and tissues. The absorbent composition of these materials means moisture is sucked away from the viruses, causing the structures to collapse.


How best to protect yourself

While many experts agree that viruses do not in fact last long outside of the body, it’s still better to be safe than sorry. Variations in the viruses in question, as well as the surfaces they’ve transferred onto, can mean that it’s better to take precautions rather than run the risk of infecting yourself. Best practice would be to spray surfaces periodically with wipes or other disinfectants, to kill all the germs present.


If you want to learn more about how you can get involved in helping us eradicate the common cold and flu viruses for good, and be compensated for your help, then get in touch today – or head over to What is FluCamp? for more information.


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