Quick question I hope,
Is a virus immortal or am I making a category error in positing the question?
Peter
IIRC, they self-destruct in order to tweak another living cell into making more viruses. So the individual viruses, at least the ones who reproduce, aren’t.
Something would have to be alive in the first place for it to be immortal. Given that viruses can’t reproduce without a host, not everyone considers them to be life.
So a Virus doesn’t qualify as life?
P
It’s a subject of much discussion.
So a hundred and twenty odd years since we’ve categorized Viruses and there is no common agreement about whether these ‘chemical phenomena’ are alive?
P
There’s no common agreement about what constitutes life in general.
Kind of buggers up SETI or SETL, search for extraterrestrial life, if there’s no common agreement about the definition of life on Earth.
Reminds me of an old Monty Python song…
P
Nope. There’s lots of stuff to speculate about, though. For churning up new information, that’s better. Here’s a 2004 article on whether viruses are alive by Luis P. Villarreal in Scientific American. Carl Zimmer wrote Planet of Viruses, if you’d like to get into it a little more. They’re fascinating.
There has been speculation that the mammalian trick of creating a placenta, which is done by a fertilized egg before it starts making an embryo and which attaches to the inside of its mother and grows into her without setting off her immune system, was derived from viral DNA that had injected itself into the progenitor genome. Haven’t heard whether that’s been supported by additional data and accepted as being true, or if it’s still speculative.
The usual consensus among biologists seems to be that viruses are biological, but are not (quite) actually themselves “alive”.
But in general, biology is messy, far messier than any of our attempts to describe it.
Anyway, even if they are alive (which is a semantic rather than an empirical issue) there is nothing remotely immortal about them. Not only, as Yllaria pointed out, do they destroy themselves in order to reproduce (or be reproduced, depending on how you look at it), there are all sorts of other ways, natural and artificial, in which they can be destroyed. I suppose there is a sense in which they don’t grow old, but that is because, on the one hand, if they are not reproducing they are not doing anything at all (they are not metabolizing or anything, they are just a bunch of complex chemicals sitting there), and, on the other, because if they deteriorate at all they are effectively done for.
Just to chime in, I occasionally see people pointing at this whole “are viruses alive or not?” question as if it’s some sort of failure of science - like if we were just a bit smarter, or worked a bit harder, we’d be able to figure it out once and for all. That’s just not true. The problem is not that we don’t understand viruses well enough. We understand them perfectly well. The question is how we define “life”. If the question indicates any sort of failure, it’s a failure of the English language, not one of science.
So either the book Everyone Poops is wrong, or viruses aren’t included in ‘everyone.’
You could say a virus “dies” when it has sustained enough damage that it could no longer enter a cell and reproduce. Without having an active metabolism a virus has no repair mechanisms; any stray chemical change in its structure might do it. I’m sure, though, that viruses vary greatly in how robust they are, how unstable they are chemically and how much damage is required to make them nonviable. In a particular environment they would have a half-life.
It’s also a problem that people really, really want there to be a firm line between “alive” and “dead”, because that distinction features so strongly in human experience, and are made uncomfortable when things like viruses and brain-dead people being sustained by machines point out that there isn’t a perfect dividing line. Viruses are “alive-ish”, and that’s all that can be said category-wise.
Oh well, y’all beat me to it, and put it better than I would, no doubt.
It’s definitely a category error, but as always, we can learn from them.
See below …
Right: they’re involved with life, but between hosts they’re mostly inert. They need to use the host’s machinery to reproduce and disperse.
Important point: the issue is “what do we mean by the word,” not “what are viruses?”
Right, even less so than an ameba or a bacteria (or anything that replicates by fission). With the latter, is one of the two daughter cells the original? If so, somewhere there just might the first cell that ever lived! It’s no longer recognizable as its original self, of course … (and yeah, I’m just kidding).
And hardly even a failure of English. AFAIK, there are only two things in this nether-region of living or not living: viruses and prions (the latter even more tenuously “alive” than bacteria). The two are different enough that they hardly bear any kind of name to group them together, other than “things that are biological, which replicate themselves (with help), but which are not considered alive”.
I bet there is a technical term or three, though. Why should vernacular English be burdened with such a term?
I know one technical term that almost suits the quoted definition above, but which doesn’t include either viruses or prions: zooids. Those are things that look like organisms but aren’t. The best example I can remember is a sperm cell.
Lol. Definitely the latter. Further evidence that they shouldn’t be considered “alive”. But they’re definitely part of “life”, just as that all that poop is.
I take it that last word was meant to be “viruses” again, not “bacteria”. I do not think there is really any question that bacteria are alive.
Please tell me that they’re not doing the pointing out. 
Here’s a paper related to that:
As always thank you all for your very considered opinions, the Dope may not always provide an ‘ultimate truth’ but it does refine one’s questions.
Thank you to to Yllaria for the link to the Scientific American article, excellent.
So are we in agreement that my original worry about the question being a category mistake was correct?
I.E. the definition of biological life cannot be applied to viruses?
Peter