Arghh I cannot figure it out and it's driving me mad! It was about some kind of serious pandemic, and the characters I remember were two women in their twenties in their London flat - I think one was a teacher and the other a nurse, who saw the first wave of sick people coming into the hospital, and the teacher ends up dying.
But there were lots of other characters too, it was one of those storylines with lots of threads. I think others were in different parts of the world but this might be wrong.
What was it?!