I watched it and while I think the beginning may be accurate, I don't think a flu pandemic would send us permanently back to the 19th century as was shown.
A flu pandemic doesn't destroy anything. Power plants, factories, oil wells, refineries, etc., are all just sitting there waiting to be activated again. Even if there was a loss of two thirds of the population, that leaves around 100 million people. Somebody who is left is going to figure out how to get those things up and running again.
It seemed to me that the experts they had on the show were actually hoping for a disaster that would permanently send us back to a 19th century society.
That's not to say that there wasn't some good information to be taken from the show. It did get me thinking about antibiotics and I'm already taking steps to fill that particular hole in my preps.