In your last sentence you state that the EMP from a nuclear weapon "was the only way to shut it down".
I'm assuming you mean that the EMP disrupts/kills the modified UA bioweapon and I mention that because it leads to some interesting speculation about a response to the modified UA.
It raises questions such as: -
1. is the electrical charge the cause of damage to the modified UA?
2. if so, can some level of electrical charge be applied to a victim of the mod. UA to cure them?
3. if that's true, what sort of devices would be created to deliver electrical charges to a victim as a cure?
4. would Tasers be sufficient for this particular application or would they need something more powerful?
5. is it the magnetic field that disrupts the mod. UA?
6. how strong does the magnetic field have to be to cause this?
7. can the magnetic field of a typical military manpack radio cause a sufficient field to disrupt the mod. UA?
8. if not, would medical devices like MRI scanners generate a field powerful enough to cure people infected with the mod.UA?
I'm assuming that either the electrical charge or the magnetic field screws up the mod. UA at a cellular level but I'm no biologist. Apparently viruses can be neutralised by screwing up their pH level and electricity and magnetic fields can have some affect on this.
According to the report released in 2000 by Michigan State University, extremely low frequency electro-magnetic fields (ELF-EMF) can cause changes to cells (to be clear though, the study did not suggest that ELF-EMF would cause health problems, only that it could promote potential cellular problems that could go on to cause health problems)
https://www.sciencedaily.com/release...1016073704.htm
So I'm basing my assumptions on that information, it is a role-playing game so I can probably get away with some imaginative interpretation!