If you were to weaponize a virus... how would you make it?
I would make it a computer virus and attack the infrastructure, not a life lost but a society totally upturned and the population untouched becoming a huge drain on resources... but even that is old school now, too.
Biological warfare is older school than nukes by a matter of a few thousand years. From dumping rotting sheep carcasses into the local well to catapulting dead cows over castle walls, that's old.
In war it was found that injuring an enemy beyond operational capacity was a much larger drain on the foe than simply killing a soldier outright so taking that one step further and leaving as many of a population alive as possible while allowing them to remain just as large a drain on demand as they always were seems to be the logical continuation of that: shut down a society and the oft cited phrase "society is only three missed meals from anarchy". Someone with COVID-19 in an induced coma may likely be
less of a draw on resources than someone sat at home wondering how they are going to pay their next mortgage bill. Just look at what happened with the toilet paper.
Even killing people is old school.
"Society is only three missed meals from anarchy". Why go through all the issues of killing a population when you can simply weaponise them? A country would be foolish to unleash a virus on the world, unless they took it to another country and released it there to make them the patsy. The new school is misinformation and using a population against their own country, convincing them doing things that will harm themselves is the right course of action. Look at a countries demographics, work out where the suggestible vulnerabilities are, and sew the seeds. You don't really need an end point, you don't need a goal as it would be very difficult to achieve a specific anyway... you only need destabilization.
A stable country is one with direction and purpose which can then use it's time and resources to effect other countries. Destabilized, it's time and resources are turned inwards to deal with the flaming fudge-bag on its own doorstep and can no longer effect other countries, at least not to the degree it once did.
Social Manipulation. Not a life lost other than those the population inflicted on themselves.... No harm done other than that inflicted by the population to itself.... No damage done other than that which the population insisted was committed in their own interests... Deniability built in because at the end of the day it's just an idea, and even if it is linked to a certain state (which would be terribly difficult to do), it is the target population who were the ones who bit on and acted on it.
The New School. Beautiful, in a way. Very, very scary in others.