He could infect the world's alcohol production, wouldn't that be fun?

Is the virus completely harmless to normal people and can normal people act as carriers for the virus?

@Bellerophon - Virus is harmless and does not infect normal people. Normal people can only act as carriers in the physical sense, unfortunately.

Put the virus spores on the toys for good children to infect their naughty siblings.

It many traditions St Nicholas does punish children that are naughty, in the Dutch tradition for example it is said he stuffs them in his sack and carries them off, or if they have been only slightly bad he leaves behind a bundle of sticks to represent a birching.

@Thucydides - Are those slavers contractually obliged to supply fertile slaves?

Those slavers have been put out of business a while ago. :)

Hi, NSA! Did you see the "modified Anthrax spores" in the question? We promise we're not plotting real infectious and deadly outbreaks.

Just going on a tangent but what happens to bad kids that stay off the naughty list in the following year? Handwavium reverse-sterilizanium?

Is there any reason beyond dramatic irony that the virus MUST be deployed on the 24th? Distributing it earlier would make this whole scenario a lot easier.

In other words, you want Liam Neeson to be Santa Claus

Are you thinking of Krampus?

I also suspect Old Nick might be a little salty because Momma Clause gave them both the same name.

I have the best idea. Evil Nick should donate super high-tech​ computers to all schools on earth. He could call them stormbreakers. Then, as soon as the children begin to use them, they release the virus! Or better yet, put tiny deathbots in all the vaccinations for school in the world, then put a transmitter on Santa's sleigh that activates it for the naughty children! MI6 will never suspect a thing!

Anthrax is not a virus, but a bacterium. Even if modified it would still be a bacterium. Do you mean anthrax has been infected by a virus? I don't know if that is possible for spores.

You mean like this guy?

@PeterMortensen - Thanks for this, I've edited accordingly.

@chif-ii - This is my Christmas Question. Timing this for the 24th is ironic license...

You know, the original St Nicholas punched someone in the face at the Council of Nicea. Just an idea for 'Old Nick' to deal with those kids who go from one list to the other every year.

No matter how you do it, you'll never get the children in Madagascar.

"So, he hoodwinks and bribes a few elves in the chemical factory and makes them create a genetically-targeted virus that chemically sterilises bad kids." Jesus, that escalated quickly...!!