How closely did The Walking Dead on TV follow the comic?

I want to read the comic, but I don't want to ruin the suspense of the TV series. Do they follow the same story? For example, I'm told the CDC arc isn't in the comics.How closely did The Walking Dead on TV follow the comic?
The general idea is followed and some of the elements in the comics are being followed in the series but not everything. In the comics, Shane dies in camp (read it and be surprised how he dies), there is no CDC, there is no Merle and his crossbow-wielding brother and there is no Dr. Jenner. So even though you have read the entire comic series, you are still in for a surprise in the TV series.How closely did The Walking Dead on TV follow the comic?
The first seasons has followed the first volume so far, but only parts of it. Some bits have been extended for the show (there is no tank, he immediately follows Glenn, and only Glenn, out of the city and into the camp). Yes, there isn't a CDC and the wifebeater and Merle aren't in the comic. Its basically taking detours from the comic, but following the same path. However, there are shocks and surprises from the first volume that havent happened yet, so only read the comic if you want to be spoiled from the future installments.