It would be horrible in real life but I thought a funny intro to a post apocalyptic movie would be a person giving a tour of a bio lab to college interns and...

"through our studies we have learned to increase the transmission rate and the death rate of the small pox virus. The downside is we had to mix it with rabies so the infected tend to get aggressive and lose there ability to rationalize their thoughts. Don't worry though, there is only this one vial of it in the entire world... these gloves are quite slippery.. Oops"

Yeah it's not that simple, wikipedia has a good summary:

Advocates of final destruction maintain that there is no longer any valid rationale for retaining the samples, which pose the hazard of escaping the laboratories, while opponents of destruction maintain that the samples may still be of value to scientific research, especially since variants of the smallpox virus may still exist in the natural world and thus present the possibility of the disease re-emerging in the future or being used as a bio-weapon.

This would kind of make sense if Isildur had taken the ring and tried to disassemble it and learn how its various magic effects worked, in order to extend life without the downsides.

The amount of things we've learned from the field of virology is fucking nuts.