What was the Bio-Digital Plague?

I like to think that what happened was this:

* All medical facilities and in every first aid kit there are nanite repositories.
* Some people installed a nanite repository in they're bodies designed to automatically cycle nanites to combat illness or injury.
* These repository's have "wifi" or similar to enable the nanites to be reprogrammed with the latest specs.
* Some creative programming was put in place to ensure that all of these repositories would always update each other if other sources were unavailable. Ensuring that all updates stuck. (delete the update and it came back via the next person to walk past)
* I imagine that technicians would be very good at coding nanites and software in general, and would have every possible safety measure in place.
* I also cannot imagine that anything coded by a human would be perfect. And either a hack or a coding error or a glitch in the coding or comm software or hardware sent out a signal that started a cascade of updates to all of these repositories.
* The "glitch" coupled with the system wide update schedules would spread to all comm gear, and from there spread unit to unit updating all nanite repositories. Those people with internal repositories or those being treated with nanites (most everyone) would be affected first. Maybe the conditions for the updated nanites to strike would not be present and if so nothing would happen to those people.
* The nanites caused the mutations to a virus/bacteria in they're unlucky hosts and an infection is born.
* The infection then spreads from person to person, infecting those without nanites and those with nanites that didn't "glitch"
* The natural reaction to the infection from medical personel would be to treat the symptoms/vaccinate with nanite therapy further complicating the situation.
* The Digital aspect being discovered, would be difficult to deal with when all comm equipment already carries the updated nanite programme and with the update being picked up again with every errant comm signal, it would take time to flush the system.
* What if the infection works faster then the mutation process. That means that the nanite host could develop symptoms 2 weeks after there dose. Those infected after could show signs in 3 days. What if the nanites slow or cover up signs of the underlying illness.
* This is a time when if your sick or hurt, nanites fix it. (They are probably programmed to stop the spread of infection first to allow people to continue their lives.) Why Quarantine?
* Scanning tech is probably linked to the update system and see mutation/infection as the correct outcome.

If the updated nanites would cause the mutation in 1:10,000 people and 1:10,000 people had nanites in their systems then in an 10 billion population then only 100 people would be affected by the nanites.
Those 100 people would infect 10 more people each, those 10 more people each. Now 10,000 people are infected! better get yourself some nanites or you could be next! say half of the people decide to do as the Government and Medical authorities suggest and boom 500,000 more infected! now there are 600,000 people infecting the population. one walks into a airport terminal, or a major sports arena. 1 million. "The nanites don't stop it". 50 million. Panic. 100 million. hysteria, mass evacuations. 1 billion. "Hay, its the nanites!" "The update is bad!", "We can't scrub it form the Comms, its in everything!", Data arch sealed (luckily it wasn't on the comm network)

Ok so now we have 9 billion people on Earth. 1 Billion dead. Who knows how many infected. All of the computers are compromised by hackers and the panicked masses. The riots have stopped, no one wants to meet anyone who could be infected. by the time the infection clears the people left alive have broken infrastructure and dare not turn on computers for fear of starting the nanites still inside survivers. How to feed the world with no computers? say 7 Billion people, even just 5 Billion? Now 1 Billion scattered to the 4 corners of the world. And that is just Earth.

What really gets me is that with how interconnected the world is today, something like Ebola or Bird flu has a real possibility of doing damage to our population level and that starts from one geographic source.