Are there any 'useful' viruses to humans?

Let me start by saying I am aware that using terms like useful, good, harmful, etc. where natural selection is concerned can be misleading and confusing; so to be clear what I mean is a virus that has some value to us as humans as opposed to what seems to be the case - viruses that are all harmful or damaging to our health.
In order to spread successfully, these ‘harmful’ viruses must not only overcome the usual obstacles, but an increasing human awareness of how to deal with them. Wouldn’t it be simpler for a virus to develop with some positive attributes, which we might well then aid in distributing ourselves? For example, perhaps a virus which resulted in increased immunity to certain other viruses, or one which stimulated a feeling of well-being or even euphoria in the host instead of making us feel horrid and miserable.
I don’t know, I’m not sure I’m phrasing this too well. I’m just wondering how it is that they’re all so… destructive towards us? Why have none become more benevolent?

Actually, there are viruses of sorts that are an essential part of our genome. Endogenous retroviruses make up up to 8% of the human genome according to some studies.

Isn’t there a theory that many organelles were some sort of parasite that got adapted into their hosts?

Also, some scientists are starting to use viruses as engineering tools. You can make a bunch of viruses and screen for the ones with interesting properties. Say some virus has a bonding affinity to a specific impurity on a surface. You can spray the viruses on the surface and see where they stick. It can be a lot easier to detect viruses than slight impurities on their own, making it easier to treat the surface.


Endosymbiotic theory. Organelles wouldn’t have started out as viruses.

The idea is they started out as bacteria.

Another is viruses can be used for vaccinations against other deadly viruses. For example the cowpox virus makes you immune to smallpox, but unlike smallpox, it won’t kill you. If a smallpox outbreak got out then finding some cowpox could save your life. When people noticed people who worked with cows didn’t get smallpox much it lead to the discovery of vaccinations.

There is a kind of virus called a bacteriophage that infects and destroys bacteria, including many human pathogens. Scientists are studying these viruses in the hope that they can find specific phages for diseases like MRSA, against which most antibiotics are now ineffective.

And of course there are viruses that attack pests, such as the Rabbit hemorrhagic disease

Outside of genetic engineering, in a natural state, from what I’ve read viruses have no good benefits to humans. Oh sure there are a few that accidently help a human but that isn’t their intent.

Unlike bacteria that can be benign or proactively helpful to humans (as well as kill them too)

I wouldn’t call a vaccination helpful in a natural state, I think it is humans exploiting a virus for a human’s benefit. Now that doesn’t mean I’m saying a vaccination isn’t good, it clearly is, but that isn’t the original intent of the virus. That is just humans using a virus against another virus.

And I’m sure there are incidental ways a virus helps but I would like to see if there were any overtly helpful ones.

For instance in the case of bacteria, there are lots of bacteria that live in our guts that do no harm to us but they don’t help us either. Well they sort of do. These benign bacteria are so numerous that when bad bateria get into our guts, the bad guys can’t live and multiply. Why? Because the benign bacteria are eating all the food and getting in the bad guys way. In other words they’re crowding them out.

Some may say that meant those benign bacteria are helpful, but I’d say they are more useful and that, at least to me, is an example of incidental help.

I think the answer is that it’s not a feasible evolutionary avenue for viruses. They must use the hosts cells to reproduce (unlike bacteria) and in doing that they inevitably harm the host in varying degrees. The virus can make you feel euphoric but if it’s killing your brain cells at the same time it can’t be “good” for you.

There are examples of viruses that are beneficial to other organisms in nature. The one that comes to my mind is the symbiotic relationship between the parasitoid wasp Cotesia congregata and a virus. The virus particles are injected into the host, Manduca sexta, along with the wasp’s eggs. These viruses help to defeat the host immune response, which might otherwise overwhelm the newly laid eggs.

It isn’t too much of a stretch to postulate that viruses could help other organisms. Though I know of no such examples, it may be possible that human viruses could help augment our own immune system against other viral or bacterial diseases.

Under your definitions, you could consider some viruses benign. Not all viruses can infect human cells.

Your point about immunization is a good one. It really isn’t a feature of the virus - our immune system is able to respond to a weakened virus and to acquire “knowledge” that allows it to respond more quickly and effectively against a future invasion from a similar virus. If not for that memory capability, no vaccines would be possible.

Well, specifically, there’s a theory that endogenous retroviruses – viruses that got into our genetic material and get passed on to our offspring – may have made live birth possible (as distinct from egg-laying).

Briefly and inexpertly summed up, the theory is that the retroviruses suppress the body’s immune reaction from killing the fetus. See a brief discussion here.

Thus viruses may have taken up the anti-abortion fight long before modern political and religious movements.

Aside from Sailboat’s (very interesting!) post above, in what way are ERVs an essential part of our genome? What would be different if they weren’t there?

I just found this, it seems that a virus was helpful to wasps at least;

The language you are using is a little misguided. “Intent” and “incidental” are powerful words when talking about such matters here on the SDMB.

I would argue on such matters that nothing has an ‘intent’ from a biological and/or evolutionary standpoint, and that everything has “consequences”; i.e., the results are just incidental.

In other words, you discount ‘incidental’ impacts (consequences), and lean towards ‘purpose’ (intent), when everything is actually ‘incidental’.

Bacteriohages were being used in the old Soviet Union to attack harmful bacteria. For example, some strains of bacteriophages (literally bacteria eaters), called T1 through T7 specifically attack E. coli. Now E. coli in the gut are benign (save for some exotic strains that seen to arise from intensive swine culture), but the same bacteria in the bladder give urinary tract infections and perhaps they could be treated by inoculations of bacteriophages. But I don’t think much, if any, effort has been espended to studying this in the west.

When I worked in a lab in the 50s we cultured both E. coli and various T-phages and took no special precautions to avoid ingesting them.

What is their intent? Who got that ball rolling?