Most viruses and bacteria evovle, but for some reason AIDS and HIV hasn't evolved yet to become airborne. Kind of scary when you think about it.
Just to clarify, AIDS isn't a virus or bacteria. It's the actual effect that HIV causes. HIV is the virus that is spread through fluids, AIDS is the disease that you can suffer from if you are infected with HIV.
And the main reason it hasn't evolved is because it is essentially untreatable. The evolution is random mutation, which likely does happen, but because the non-airborne variety of HIV still exists en masse and can't be removed by treatment (And if it were, it is likely the airborne strain would be affected too), any airborne strains that do come about from random mutation, are outcompeted by regular HIV.
Plus, the chances of it becoming airborne is very slim, in comparison to it mutating to have no actual change in the way it works. It's very likely to mutate, but that mutation doesn't guarantee a change in how it spreads.
It's a bit like the chances of your own human cells mutating (which is very common) to have absolutely no change in the way the cell works, is a much higher chance than of the cell mutating to be cancerous. Obviously cancer mutations do occur, but a cancer cell can't be outcompeted by a regular cell, so that's why you see cancer crop up.
Also bear in mind that HIV is a virus. And Viruses can not be treated with antibiotics as they infect inside of cells. It is entirely down to the bodies ability to combat the virus with it's immune response. And since HIV is the Human Immunodeficiency Virus, and it specifically attacks your immune system, rendering it obsolete, it's difficult for it to be removed.
Viruses will evolve (these days) slower than Bacteria, because Bacteria will have the effects of antibiotics to combat against. If a bacteria randomly mutates to be immune to an antibiotic then it has a useful evolution. If a Virus evolves to be immune to an antibiotic, then it makes no difference to it.
Also, Bacteria can spread their own DNA between each other and through different species of Bacteria. Viruses can't.
More on-topic however; I don't think it's a bad idea. Preparing for any sort of event is a good decision for the military. Once it's all over and done, they've just completed a large military practice. They've gained experience in working together and working in unusual environments.
Yeah, they might have been fighting "zombies", but they could have been anything, from drug-induced psychos, to people effected by some sort of viral outbreak or pyscho/neuro-toxic gas, say launched at the country by an enemy, or what not.
The chances of a zombie "invasion" in the style you see in movies, where for some completely unknown reason the Dead themselves come back and infect the living, that is unlikely.
But there are chances of having to combat areas that have been affected by disease or other strange effects.
Or there is simply the high chance of the military having to be ready to combat some enemy or do some mission within the different locations they'll be practicing in.
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