Fact: germs don’t obey “rules” like The Five Second Rule (and if that’s news to you, sorry to burst your bubble). But even if pathogens infection rates don’t follow arbitrary parameters like that, what amounts of time ARE we talking about? Seconds? Days? Years?

In other words: how long do germs actually live? What is the lifespan of germs?

**One quick note: in microbiology, the term “live” gets pretty tricky. Umbrella terms like “germs” or “pathogens” usually include viruses, which scientists don’t consider to be alive. However, lumping them all together is also the simplest way to talk about the subject. So, for the purposes of this post, we’ll be using “alive” to mean “active” or “capable of infection.”

Now then. On to the question. And unfortunately, if you came here looking for an easy equation to plug into an infection stopwatch or something, you’re going to be disappointed—because the answer is a clear, unambiguous “it depends!” It’s estimated that humans come into contact with upwards of 60,000 types of pathogens on a daily basis, and there’s a staggering amount of genetic diversity between individual microbes.

On one end of the lifecycle spectrum is the human immunodeficiency virus (HIV), which usually perishes as soon as it’s exposed to sunlight. On the other extreme end, bacteria like Bacillus anthracis (anthrax) can survive independently for dozens—or even hundreds—of years. And between those two endpoints, pathogens cover just about every duration in one form or another.

Also, remember that this is about more than just a singular virus or bacterium’s lifespan. Almost always, we’re talking in terms of colonies—which means we need to consider the speed at which the colony reproduces. On the whole, bacteria take the crown for the fastest growth rates, with some colonies of Clostridium perfringens able to double their size in under 10 minutes.

To complicate the answer even further, a pathogen’s biology isn’t the only variable involved here. Lots of environmental factors can extend or shorten germ longevity, including:

• Temperature (many germs like room temperature)
• Humidity (many germs like moist environments)
• Acidity (many germs like neutral surfaces)
• Surface type (germs like flat, non-porous surfaces)
• Sunlight (germs don’t do well with ultraviolet radiation)

In short, there are a lot of factors in play, and it’s just about impossible to predict the lifespan of germs in your home. But for most households, the practical answer is much simpler: don’t worry about germ lifespans. Seriously.

Sure, there might be some useful information to be gained from the factors we’ve explored here. But as a rule of thumb, if you’re trying to put a clock on how long to wait before touching a previously infected surface, you’ve probably got bigger things to worry about. Rather than trying to count down the seconds before a germ self-destructs, use the available tools to get a proactive edge in the fight against pathogens.

After all, it doesn’t matter how long they live if you can wipe them out right now.

Related Questions

Hang on. Viruses aren’t alive?

Nope. Or, at least, mostly nope. So long as they’re floating through the universe without a host cell, viruses are definitely not alive — they’re just inert clumps of genetic material within a protective protein shell. They don’t move themselves; they don’t generate energy; they don’t reproduce. They just are. When they attach to a host, however, they coopt the cellular machinery to do the work of reproducing for them. The dead-or-alive line gets pretty blurry when it comes to viruses, but science currently doesn’t consider them to be alive.

So then how do I fight germs effectively?

For starters, there are the easy methods: wash surfaces regularly, use antibacterial soap when necessary and change out your sheets and towels often. But that only does so much (especially against viruses). That’s why experts recommend fortifying your home’s germ defenses with UV-C air sanitizers to neutralize all the nasty germs that soap can’t kill and water can’t clear.