The term “germs” isn’t just a catch-all for dirt on surfaces you don’t want to touch. Instead, germs are organisms that fall into four main categories: bacteria, viruses, fungi, and protozoans.
For the most part, germs are harmless. They’re all around you, and no matter how clean you are, you’re going to come into contact with germs regularly. Usually, that’s no big deal. However, there are also some problematic disease-causing germs out there. These are known as pathogens.
Those harmful germs are the ones you’ll want to avoid coming into contact with. But because pathogens can live on many different objects that you touch every day, avoiding them can be difficult.
So, which surfaces are most likely to harbor pathogens, and for how long? Here’s what you need to know to avoid pathogens as much as possible throughout the day.
Which Surfaces Do Pathogens Thrive On?
Pathogens evolved to live in or on hosts. Outside of a host, pathogens can’t live forever. However, they can stick around on some surfaces for quite a while before reaching their next host.
How long a pathogen can survive on a given surface depends on the type of pathogen, though. In general, just about any surface can harbor pathogens. However, viruses (such as cold, flu, and coronavirus) usually live longest on hard surfaces, including plastic and stainless steel. Meanwhile, bacteria often thrives on the warm moist environment provided by dirty fabric, such as clothes and bedding.
In short, nearly any surface can serve as a temporary host for pathogens of some sort. Just because it looks clean (like stainless steel) doesn’t mean it can’t transmit disease. Other variables also affect the lifespan of pathogens: for example, sunlight threatens some pathogens but not others. And, generally speaking, humidity is pathogen-friendly—very few microbes can survive on completely dry surfaces.
The Lifespans of Common Pathogens
With so many variables, how can you possibly avoid pathogens?
The answer is that you can’t—at least not completely. Still, best practices like handwashing and cleaning certain surfaces often will help. To get a sense of the wide variety in pathogen lifespans, here’s how long to expect common pathogens to survive on surfaces.
A number of pathogens can cause what we call colds, but the most common are rhinoviruses. Generally speaking, most of these viruses are no longer infectious after remaining on a hard surface for 24 hours.
On soft surfaces, the virus is neutralized even faster. This means that a doorknob can actually harbor the cold virus longer than a dirty kleenex can.
The flu virus is more dangerous than the cold virus, in terms of negative health effects. But the good news is that it usually has a shorter lifespan.
One study found that two flu virus strains were no longer viable after just nine hours on a hard surface. And, on soft surfaces, those viruses were gone in four hours.
The big question nowadays, of course, is how long does the coronavirus live on surfaces? This virus is highly contagious and more dangerous than most common pathogens, so researchers have devoted serious effort to answering that question.
So far, studies have shown that the coronavirus can survive for up to three days on stainless steel and plastic, and up to 24 hours on cardboard. Researchers even found that the virus could survive for half an hour in aerosols before drifting down and clinging to surfaces (although in ideal lab conditions it stayed afloat for three hours). These relatively long lifespans help explain why the coronavirus has spread so fast.
Salmonella is a type of foodborne pathogenic bacteria. However, it can survive even outside of food and hosts for a while.
On a dry surface, most salmonella strains will remain infectious for up to four hours. However, at least one species appears capable of surviving on surfaces for as long as four days. Keeping kitchen surfaces clean is especially important to reduce the spread of foodborne pathogens—and soft surfaces like kitchen sponges and towels are particularly bacteria-friendly so be sure to sanitize, launder, or even dispose of (in the case of well-used sponges) them frequently.
Some pathogens can’t be transmitted by touching surfaces at all. Malaria is one example.
Malaria is most often transmitted via mosquito bite. The malaria protozoa first infect a mosquito, then gets transmitted to a human host when the mosquito feeds. This pathogen can also be transmitted via organ transplants, blood infusion, shared needles, and other forms of transmitting blood. However, you can’t get malaria simply by touching surfaces or hanging out near someone else who has it.
When you talk about germs or pathogens, you’re talking about a long list of microbes, all of which have different lifespans in different places. That’s why there’s no one universal approach to reducing the spread of pathogens.
Despite all the variables at play, the best defense is to avoid touching your face (where pathogens can easily get into your mouth, nose, or eyes) and to regularly and thoroughly wash your hands. On top of that, make sure you are regularly disinfecting the surfaces you come in contact with, and leaving the disinfectant on for long enough to get the job done.