So why aren't there any beneficial infectious bacteria/viruses?

I know we have tons of bacteria that help us all throughout our bodies all the time. I mean something that causes a temporary infection, like a cold only something that helps you in you some way. Why don’t any bacteria release endorphins or make your sweat smell like pine trees or give your hair red highlights? There was an episode of Red Dwarf that had ‘positive viruses’ that gave you luck or sexual magnetism, but that’s pretty extreme. I can see them doing something marginally harmful too, like a cold, but if they had some side benefit people would be lined up around the block to catch them. They’d never go away. It would be the ultimate in survival characteristic, a disease the host wants to catch. So what would prevent this from happening?

There is some indication that hookworms may cure or control IBS and asthma.

Does that count?

Mitochondria, without which modern cells could not function, are modified bacteria. This could be considered an example of a beneficial infection - one so beneficial that it’s become essential to life.

A big reason is your immune system. A lot of the symptoms you associate with viral infections - swelling, fever, etc - are actually side effects of your immune system launching into action to fight off infection. Your immune system doesn’t stop to wonder, “Hmm, I wonder if it would really be that bad to let this guy in”. It just attacks. A mutually beneficial relationship would almost certainly require a great deal of time for the two species to coevolve (as presumably happened with the mitochondria way back when), and our immune systems just won’t let that happen.

Now, it is true that there are probably a lot of viruses that have no effect on us whatsoever, sneaking under the radar in various ways. Indeed, this is really the ideal evolutionary scheme for a virus, and a huge chunk of the human genome appears to have come from viruses that have integrated into our systems. And there are our normal commensal bacterial species in our guts and on our skins that arguably have important benefits for us, but they live on us, not in us, if you consider that an important distinction. But I’m not aware of any transient infections that provide benefits.

Ah, this makes sense.

Doesn’t “infection” imply “non-beneficial”? There are hundreds of beneficial bacteria in our bodies, but because they are beneficial, we don’t refer to them as “infections.”

Yes. Infection means detrimental colonization of a host by a pathogen.

Many bacteria live in your body and perform essential job functions that keep you alive and healthy. You aren’t infected with them, because they are not identified as foreign bodies by your immune system, but antibiotics attack them like any bacteria.

Bacteria play roles in digestion, joint health and even artery and heart health. Overuse of antibiotics, which attack as if these beneficial bacteria were infectious, can lead to all sorts of issues.

Oh. I was using that word to differentiate bacteria that you acquire temporarily vs bacteria that are with you constantly. I imagine since there isn’t a temporary beneficial colonization, there isn’t a different word for it?

Well, there’s the term “occult infection”, which refers to infections which cause no symptoms. Rubella infections in males would be a good example- we can carry the virus for years and years with no ill effects.

I don’t know if there’s a word for the good kinds of bacteria, though, like the ones that live in the gut and aid digestion. Probiotics is often used to refer to them. I don’t know if it’s a catch-all though.

ETA: I just realized you’re talking about whether there’s a different word for long-term infection as opposed to temporary ones… and I have no idea.

Gut flora. I also heard a talk where they used viruses to restore photoreceptors in monkeys.

As mentioned, there are a number of harmless or even beneficial bacteria. Viruses are a little trickier, since by nature, they have to harm or destroy a cell to reproduce. They have to infect a host cell and then break open that host cell to be released. Some bud off, but even in that, they take a piece of the host cell membrane. Also, anytime the host cell’s DNA is altered, the risk of cancer is present.

That said, there are a couple of viruses, that are, if not beneficial, at least non harmful, even when infecting humans.

>Red Dwarf that had ‘positive viruses’ that gave you luck or sexual magnetism

T.gondii affects human behavior. It makes women more outgoing and potentially more sexual. Short article here:

Someone wrote a paper that argues that toxoplasmosis helped bring about human cultural diversity.

There are all manner of behavior altering parasites that affect both humans and animals. Carl Zimmer wrote an excellent book about this called Parasite Rex.

If they’re beneficial, why would the infection be temporary? Those bacteria which are good for us, like the ones which assist in digestion, our immune systems have evolved to not attack. The bacteria don’t want to move out, and our guts don’t want to evict them, so why wouldn’t they stick around?

Bolding mine.

If you have any cites handy, I’d love to learn more about that.

Because it’s difficult to explain to your immune system that you want the beneficial effect it’s causing. Imagine a mild flu strain that caused sweating, but either altered the sweat glands a little or released a waste chemical that caused your sweat to smell like fresh cut mint or pine or whatever. Your body would fight off the infection, but the by-product is at least somewhat beneficial.

:eek: Wow, that there is messed up. That’s kind of what I’m talking about it.

That’s fascinating. Thank you.

Also, kinda disturbing. It’s sort of like the movie Species writ small.

Nah, it’s easy to explain that to the immune system, it just takes a while. In the natural course of events, some peoples’ immune systems will fight off that infection, and some won’t. If it really is a net benefit, and the minty fresh scent is more significant than the flu-like symptoms, then the people who didn’t fight it off will be more successful in reproduction, and the next generation will have a greater propensity towards the minty-scent virus. Lather, rinse, and repeat, and eventually everyone’s harboring the thing.

Exactly. So why don’t we see these things now, before they get integrated into our bodies? I think T.gondii qualifies, if that’s really what’s going on here.

That has to be one of the weirdest link I read on this board. Brazilians are more sexual than Britons because a fucking parasite wants to make its way to a cat??? :eek:

What will we learn next? That the real cause of WWII was a virus attempting to infect a rhododendron?

It isn’t April’s fools day, is it?