> In fact, if your host lives for as long as possible without suffering any negative effects from your freeloading, is preferred by mates and most loved by peers, etc., that's when you spread the furthest.

Ah, you mean toxoplasma gondii. Heh.

Sure, that's one example:) Wouldn't say it is trying especially hard to make its host survive the longest (motorcycle accident anecdata and such) but it surely isn't killing it too fast.

Worth noting, seeing as it evolved to survive by cats and rodents, it is probably accidentally well-adjusted to humans (luckily we are not super different from rodents I guess). If it was as infectious as flu and had similarly mild effects it has now I'm sure most would be having it.

I wonder if some of the "worse" diseases are similarly mild to their animal hosts (birds and such), and us humans are just not as lucky to be similar enough in relevant aspects as with rodents and toxoplasma.

It changes both your appearance and behaviour to literally make you more attractive, but at the same time less fit depending on what you count. Also, it may be connected with schizophrenia.

Not to make me attractive. To make rodent get eaten by a cat. Supposed attractiveness of humans with latent toxoplasmosis is an accidental side-effect, since it does not transmit between humans it is entirely pointless.

> If you were an infection that wanted to survive and spread as far as possible, you wouldn't want to kill your host at all.

You may be oversimplifying here... consider that the host has an immune system and the infection has a limited time to either live in the host or to kill the host and remain in an infectious corpse for a while longer afterward.

I mean, somehow toxoplasma seems to not be caught by the immune system, so presumably they can evolve this way. If you don't directly harm the host, and maybe even benefit it, its immune system would have bigger fish to fry than going after you, no?

As to corpses, fair enough. Ah, if only these infections caught up that humans don't often just leave bodies around...

Sure, its maladapted where the common cold virus is much better adapted, and the bacteria which live in our stomachs are the best adapted of all: they just co-opted us as hosts.

But, along the road to perfect is good enough: If you can get along the silk road, you're doing ok.

> bacteria which live in our stomachs are the best adapted of all

Mitochondria would like a word… I mean, almost all eukaryotes have 'em.

Did they co-opt us, or did we enslave them?