In AMC's The Walking Dead, how did the flu take out so much of the population? Me and people I've known have gotten plenty of them. The only time I hear of them killing people is extremely weak and frail children or elderly people. They are also not treatable via antibiotics AFAIK. The people seemed to be able to stay warm, have a ready supply of clean food and water, possibly vitamins too.
How would so many apparently healthy adults fall to a realistic strand of flu that exists in real life?