Are all viruses pathological?

kw: viruses, medicine

In a recent article in Wired (found here at wired.com), the question is raised, if we develop broad-spectrum antiviral medications, should we use them? Since the publication of that article just a month ago, about sixty online articles have explored the idea. You can find them and other similar articles by searching for "beneficial viruses" (include the quotes for a phrase search).

Are all viruses bad? Do they all cause disease?

When bacteria were first discovered, it was thought by many that all "germs" were bad, and once antibiotics began to be developed in the 1930s, they were used indiscriminately for any sign of infection. Such things as upset digestions, diarrhea and bloating were thought to be unfortunate side effects. But it didn't take long for our "internal flora" to be discovered, and we are still learning how important they are. The list of beneficial bacteria, some residing in our gut, some on our skin, some lining our sinuses, and others who knows where, continues to grow. By current estimates, 90% of the cells in a "human" body are bacterial, though they make up no more than 2% by weight.

It is no more than a decade or two since it was discovered that in a typical sample of ocean water, there are a thousand virus particles ("virions") for every eukaryotic cell, most of them being bacteriophages. Or, I should say, denizens of bacteria, because it is not known whether a virus residing in a bacterial cell is there to kill it or in some way to help it. We know that phages are pathological to bacteria, just as many viruses that infect us and our animals and plants are pathological. But we are just beginning to learn of viruses that are found in cells yet don't seem to cause disease.

Wouldn't it be ironical if we developed a broad-spectrum antiviral, tried it out, and found it to be universally fatal to the mouse, monkey or man into which it was introduced? Fatal why? Because it eliminated a virus to which we play host, that performs a required function! Fortunately, while our internal flora of bacteria may be helpful, none is required for us to continue living. Strains of supposedly germ-free mice have been developed, and though they live differently than ordinary mice—mainly in that they need to eat more—they seem to live well enough. But we don't even know if those mice are virus-free. We don't yet know how to produce a virus-free mouse, or if it is possible to do so.

The days of effective antibiotic medicines are drawing to a close. We are being forced to take another look at an older, effective, if cumbersome, therapy using bacteriophages. The problem is, these are very specific. There are no broad-spectrum phages. A second kind of therapy (this is very early days) is the anti-bacterial bacterium: using an overwhelming dose of our good bacterial companions to drive out those we don't want.

This makes me wonder, are there anti-viral viruses? Are we actually host to any (or many?) viruses, not yet discovered or studied, that keep pathological viruses in check most of the time? Just as certain bacterial are becoming known as essential ingredients in our immune function, there may also be immune-functional viruses.

This just scratches the surface of the questions we need to be asking about viruses and our relationship to them. There is a long way to go, and we ought to be careful how we use new "miracle" drugs, lest the miracle we perform is to our own detriment.