Your apocalyptic theory is fearfully true. Our ecoshpere is very fragile. One event could set the dominoe effect. A comet lands in the ocean and poisons our fragile food chain. A stock market crash could go worldwide. Think how dependent we are on electricity. What if suddenly it was all wiped out. We are more fragile than we know.
On the other hand note...aren't monkey's immune to AIDS? If they could figure out which gene makes that immunity...I should stop.
And you are right, we are too fragile. I always tell my friends this and they think i am fibbing with them. Infact i got them a book on survival and all that stuff. The thing is we are too 'civilized.' Imagine what would happen if the world as we know it ceased. For example if there was a major terrorist attack in the US (considerably bigger than 9-11), and the services we are so used to went away for awhile, society would just crumble! Imagine if a region has no electricity for days, no running water, if all the food in the supermarkets was looted, if mobs roamed the streets, if everyone was afraid of everyone. Imagine if one couldn't call the local Pizzeria for a home delivery, water was no longer available with the twist of the wrist, warmth was no longer a given, dialing 911 only led to static, and the large glass windows that were once so beautiful only serve as a beacon to all forms of social dregs to come crashing through!
What about Martial Law and the national guard? Wouldn't they patrol the streets and keep the order? Well, if the incident (be it a biological attack, large-scale natural disaster etc) was large enough, they would be inundiated and spread too thin. And if it was a truly enormous event then they would just go home to protect their own families.
You'd be surprised how far sane people would become raving lunatics if their environment was changed into something alien and uncomfortable. Probably the worst place to be would be in suburbia. It would be basically tantamount to a zombie attack (and if you really think about it, all those cookie-cutter suburbs: ie the same exact houses, all with labradors, a sedan, a minivan, kids that dress and talk the same, group think etc) ......
Anyways, let me stop my rant before some start thinking i'm crazy.
As for the monkeys and their immunity, the reason they are immune to their version of AIDS (in that the Simian Immunodeficiency Virus - SIV - doesn't develop into a full blown terminal stage) is due to their developing resistance over the eons. You might be interested to know that certain prostitutes in central and east Africa were discovered to have amazing resistance to infection with the AIDS virus. Their number is very small (last time i checked it was around 30), but scientists say that it probably happened in the last decade or so. Apparently during sexual intercourse they go enough virii particles to register in their systems (with T-cells responding), but at the same time not enough to be able to start an infection. This is, obviously, quite rare. But there is a small pocket of prostitutes that is resistant to the disease.