tl;dr: About two weeks ago a artificial protein was introduced into the environment that makes humans immortal upon ingestion and a short 'incubation period' while it replicates throughout the body. As a result (You) are now immortal - ALL of you.

I am a secret multibillionaire who has worked in the shadows under multiple identities for decades. I run a secret organisation tasked with solving world problems. This was one of our long-time projects, and we had ample time to consider how such a thing should be deployed.

We foresaw that if such a cure for mortality were ever created elites would rush to monopolise it, or at least make sure they were first in line for it at the expense of other equally deserving human beings. Also there would be endless debate about consequences and other political delays while good people died unnecessarily.

To avoid this kind of unfair distribution I decided long ago that if there were anyway it could be deployed as "non-consensual freeware" then that's the way it would be done. I take full responsibility for this decision, to impose immortality upon every individual on Earth. Many people will have objections, some quite valid, and for that I am truly sorry. I'd prefer not to make a unilateral decision to force this upon everyone, but on balance I just don't really know how this kind of thing could be done fairly otherwise.

In the coming weeks you will start to notice your own health improving and disease and death rates dropping precipitously. Of course nobody will really believe it at first. Some people with severe biological damage cannot be repaired in time, so some people will still keep dying for a while. As well as by severe accidents, no protein can fix getting hit by a bus I'm afraid. But normal aging, and most diseases/disorders the average person would ever get during their lifetime, are now a thing of the past.

I think history will remember me fondly, but oddly I still feel the need to ask you to forgive me.