Surface Contamination

Excerpt from Dr. Gavin Macgregor-Skinner article in ISSA Magazine

One of the most common questions people are asking these days is: How long do infections viruses and bacteria live on surfaces? 

Viruses and bacteria deposit and exist on surfaces indoors of virtually any facility, they can also remain viable for hours, or even days, dependent upon the fomite material, microorganism type, and indoor environmental characteristics.  

Like everything in life, the viability of a virus or bacteria is a function of molecular structure.  Viruses are not really "alive" because they cannot reproduce by themselves.  So instead of asking how long a virus or bacterium can live on a surface, we should ask how long they remain infectious.

According to the EPA, American's spend 93% of their lives indoors. That means only 7 % is spent outdoors, or only one half of one day per week in the fresh air. We are basically an indoor species.

People often think the reason we get colds and flu more often in the winter is because it's cold outside.   This is false.  We get colds and flu more often in the winter because we are generally indoors, where the humidity is lower and we are exposed to higher concentrations or airborne pollutants, including cold and flu viruses.

What is a fomite?
The potential for transmission of bacteria or viruses in by indirect contact (i.e. via fomites) is linked to their ability to survive on commonly touched surfaces. However, although there have been studies, big gaps remain in knowledge, evidence, and data on this subject.

What is a fomite? A fomite is any inanimate object that may be contaminated with infectious agents and serve in their transmission and spread disease.   These inanimate objects carry germs that cause infection.  Examples would be: cutting boards, kitchen sponges, toothbrushes, cups, the floor, etc.   Bacteria and viruses can remain infectious for a surprisingly long time on almost anywhere you may touch, even inside refrigerators and freezers.

There is limited information on how surface contamination is transmitted by human touch.   When we touch an object, we transfer bacteria or viruses to a surface or accumulate more bacteria or virus on our hands. A contaminated surface can be touched by a number of people, and each of these individuals subsequently touch other surfaces as they move around.  Each of these now contaminated surfaces can be touched again by other people, and so the touching sequence continues. 

We know that contaminated surfaces and objects can transmit disease agents, and that discarding  contaminated objects, surface cleaning and disinfection, and hand washing with soap or hand sanitizer, can decrease the risk of infection. 

Research has shown that surfaces in crowded indoor environments have measurable levels of viruses.  Most research has focused on the flu, but similar results are found for norovirus, SARS, and MERS.  These studies and many others confirm that viruses that are known to cause communicable diseases in humans are commonly found on surfaces, but it must then be determined whether they are viable and potentially infectious to humans. 

Virus Viability 
A study entitled Survival of influenza viruses on environmental surfaces in the Journal of Infectious Diseases tracked the viability of influenza  viruses on various surfaces, finding that they remained infectious up to 48 hours on hard, non-porous surfaces, such as stainless steel, plastic and up to 12 hours on porous surfaces, such as cloth, paper, and tissues.  Moreover, fomite transmission of influenza viruses was considered possible because influenza viruses  could be transferred from stainless steal to hand from up to 24 hours after contamination, and from tissues to hands for up to 15 minutes after contamination.  The viruses subsequently survived on hands for an additional five minutes after transmission.

A study concluded that the human corona viruses can remain infectious on surfaces, outside the body, at room temperature for up to nine days. Another study in March 2020 found that the virus can survive for up to three days on stainless steel and plastic, four hours on copper, and up to 24 hours on cardboard. However, the amount of viable virus decreased much more quickly than that, and we need to be exposed to a certain 'dose' before becoming infected.  But sometimes a small amount is enough. More research is needed in this area.