Germs: pretty much everywhere
November 7, 2009 5:37 AM   Subscribe

Epidemiology-and-Germ-Theory-Filter: are bacteria, viruses, fungi, etc. that cause common conditions (such as warts, conjunctivitis, and ringworm, for instance) pretty much everywhere (already)?

The relevant literature suggests that they are fairly contagious, and spread by contact. But while one can take precautions towards limiting contagion, doesn't it seem that given the prevalence of these diseases and the lack of precautions most people take, that the agents that cause these diseases must already be pretty ubiquitous, and that the only reason that not everyone has warts and pink eye is that people's immune systems are functioning properly?

In other words, am I right in saying that: although you probably want to avoid wrestling nude in the shower room at the Y, and farting bare-assed on people's pillows, people usually get warts and pink eye not because they failed to take these precautions, but because the germs that cause them are already pretty much everywhere, and happened to catch these people on a bad day, immunologically speaking?
posted by Busoni to Science & Nature (6 answers total)
I think the issue is how long the germs and whatnot last in the environment. They probably are out there all the time, but they are also probably dying all the time too. So your physical and time proximity to an exposed person is much more of a vector.
posted by gjc at 6:06 AM on November 7, 2009 [1 favorite]

A lot of germs are already in or on you - and have been since birth. In fact, the only way to avoid bacterial colonization is by C-section birth and then living in a sterilized bubble and eating only autoclaved food. So a lot of things that can make you sick already live inside of you, but your immune system is very good at keeping things at bay. Unless you are bubble boy, you probably already have potentially pathogenic bacteria living inside of you, waiting for the right moment to attack you, or jump onto someone who is more susceptible.

So in short, yes, your immune system is pretty awesome. Almost all pathogens work by using very specific strategies to evade it. But, it is possible to overwhelm it, or that your immune system has a very slightly different than someone else around you, making you susceptible to disease from something that is not harmful to them.
posted by fermezporte at 6:55 AM on November 7, 2009

I'm sure that many people can come up with examples of two different people they know, leading similar lives (in terms of germ exposure) but one is always sick and another has supposedly never been sick a day in their life.

An interesting sort of flipping around of your question, regarding immunity taking precedence over exposure, is the realization that early exposure itself leads to greater immunity. So its not just that germs catch some people on a bad day but that some people have immune systems which are more experienced in a sense in dealing with this type of potential infection.
posted by vacapinta at 8:16 AM on November 7, 2009 [1 favorite]

There are some cases where this is true (Candida) and some where it is not true (Adenovirus). In any case, the larger the dose of pathogen you're exposed to, the more likely you are to get the disease, no matter how awesome your immune system. Wash your damn hands.
posted by molybdenumblue at 8:31 AM on November 7, 2009 [1 favorite]

Wow, you've already got some great answers. I would add that old rule about washing hands frequently, soap and water for long enough to sing "Happy Birthday" (20 seconds?), and dry them off. Also, never touch your eyes.
But yes, germs are everywhere.
posted by bebrave! at 10:13 AM on November 7, 2009

If you want a good list of the things that are REALLY everywhere and you'd definitely get if your immune system wasn't functioning properly, look at what people get when their immune system is shot. These are called "opportunistic infections," meaning that the pathogens are always around, but they can only cause infection when the opportunity of a weakened immune system presents itself. For example, people with AIDS face candida (yeast) infections, cytomegalovirus, mycobacterium avian complex, and fungal pneumonia, among other things.

There's a great list here of normal flora (that is, bacteria and fungi that live on pretty much every person alive and normally don't cause a problem), and the ones with asterisks can cause infections if your immune system goes down.
posted by vytae at 11:03 AM on November 7, 2009

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