[Dagda (OP)]

I'm working on a science fiction piece set approximately in the modern day, and I was hoping to explain certain plot elements as being the result of a fictional virus. However, I'd also like to avoid having said virus just be deus ex machina by another name, with ridiculous abilities handwaved by a bunch of nonsensical technobabble. Since biology 101 and Wikipedia are only going to get me so far, I'm trying to ask around elsewhere.

For starters, I'm hoping to get an idea of whether each of the following concepts are realistic, outlandish or downright impossible:
-Scientists being able to create a virus, or at least deliberately modifying elements of an existing one to suit their purposes.
-A "benevolent", non-infectious virus that improves/augments/causes muscular hypertrophy (The growth of muscle cells).
-A virus that affects more than one type of cell.
-A virus that has at least a limited effect on most mammals.

Thanks for your time.

[another_someone]

Modification of viruses is an ongoing practice.  In its simplest form, this was crudely what is happening with many vaccines, but it is a fairly indiscriminate modification.  More recently it is happening as a vector for experimental gene therapy (modified viruses are used to allow human cells that are unable, through genetic defect, to properly make some protein, to be able to start making that protein).

I see no reason why viruses could not be used to promote muscle growth, although I would be dubious about assuming that genetic manipulation alone could allow that growth to happen in a an appropriately controlled manner - but genetic manipulation through viral infection, combined with an appropriate exercise regime would probably work.

As for the final point, I am not totally certain about.  Some viruses, like the flu virus, seem quite happy to move between animal populations (although it must be noted that they do not limit themselves to mammals - and hence the risks of avian flu).  On the other hand, they are generally specialised for one species, and do usually require some mutation to become properly infectious in another species.

In general, bacteria and fungi are more indiscriminate than viruses.

One word of caution - I don't know how you are approaching this matter, but a lot of people writing about scare stories about infectious diseases use the shock effect of a disease that kills its victims quickly.  The most dangerous diseases are those that kill their victims slowly, that remain dormant for a long time, so giving the infected person a long time to infect other people before they themselves become aware of their infected state (and a corpse is very much less likely to infect anybody - particularly so with viral infections, which normally cannot survive long outside of living tissue).

[Dagda (OP)]

Actually, the inability of the virus to properly control the muscle growth is going to be one of the major plot points- well, perhaps I should explain further.

The short of it is that I'm trying to come up with an explanation for the classic "zombie" scenario that isn't completely lies and flimflam, similar to what's been done in other recent zombie stories like 28 Days Later- in fact, the basic idea I'm working with would be taken from the Resident Evil series of videogames.

In that series, the zombie-creating "T-Virus" is said to have been created by combining what we'll call Virus A and Virus B. Virus A was the result of a failed decades-old project to create a "super-soldier" virus that would physically enhance the subject and also accelerate the rate at which they heal. That project was classified as a failure because, like you speculate, they couldn't keep the virus from leading to uncontrolled growth and mutation.

Virus B was a strain of Ebola- the cinematic type, like you allude to. They were trying to come up with a way to use it as a biological weapon, but while this strain was oh-so-lethal and nigh-unpreventable they just couldn't give it any real incubation period and in true movie fashion it killed its victims far too quickly for it to spread. So they had the bright idea of combining it with Virus A as a way to keep the host alive longer. Zombification was the unexpected result- the victims didn't quite die, and were in some respects more able-bodied than before, though the same can't be said for their mental well-being.

Of course, if I go into any more detail I'll be forced to bring up all the patently ridiculous parts of the story that I've been ignoring or glossing over- including the fact that Resident Evil uses this explanation to justify things like a subject undergoing a series of "transformations" that double their body mass in a matter of seconds.

[Andrew K Fletcher]

Dagda

All living cells when take away from our relatively stable 1g Earth environment mutate, particularly aboard the space laboratory in micro-gravity, there is a huge amount of evidence to support this and it is common knowledge. So if reducing the amount of gravity on the growing organisms changes their cellular structure, it is quite possible that the same experiments on a planet that has say twice the gravitational force as the Earth could modify the same organisms beneficially and create superior enhancements in muscles and bone.

I need to talk to you in order to get this across, because of my own research into how gravity affects all living organisms. I believe I can show that the heart does not need to pump fluids around the body in order for the fluids to circulate, gravity could do this on its own, so it can be shown in your film that a heart could stop functioning and during the shutdown circulation can be restored without the heart and could even flow in the opposite direction to the normal blood flow, all that would be required is a density change in the fluids at a give point in the circulation to initiate it. Fact or fiction?

Fact: Male Bull Terrier Heart stopped many times during walks. All that was required to enable his heart to beat again was to raise his upper body. Though it pained me to let him go eventually, all I had to do was to leave him horizontal and he passed away as anticipated.

An elderly lady had no evidence of a pulse, yet her blood circulated and completely baffled her doctors when she continued to live for many years after receiving a negative prognosis.

When we are conceived there is no heart beating, yet fluids circulate. When we are born, immediately we take our first breath, the direction of our blood flow changes.
When we die, circulation does not stop it continues driven by the process of decay. What is driving these fluids if it is not the heart? Answer it is gravity!

Andrew K Fletcher

[shrewbolt]

...If only people were that simple. Oh, hang on...

[MayoFlyFarmer]

all of your questions are hypothetically true, except for the one where you described a "non-infectious virus that aaugments muscle cell growth"  for it to have any effect on muscle cells, it would have to infect them and could thus not be "non-infectious".  But i think thats just a matter of wording.  I think what you would want is a non-replicating virus.

the most unprobable of your hypotheticals, is that a virus could infect most mamals.  while this is technically possible, it would have to be a very special virus.  most viruses are limited to a very narrow range of hosts.

[Kryptid]

The rabies virus is a good example of a virus that affects a broad range of mammals. Interestingly, spotted hyenas can carry the virus but do not show symptoms of rabies.

[blakestyger]

There is a film 'Code 46' with Tim Robbins and Samantha Morton that explores benevolent artificial viruses (as a side issue) that you may find useful.