In terms of ratings, HBO's "True Blood" is starting to look like the "ER" of premium cable.

 

Alan Ball's vampire soap notched another series record Sunday night, attracting 5.3 million viewers, according to Nielsen data. It's the fifth consecutive week "Blood" has delivered a record performance for HBO.

 

More impressively, "Blood" saw its numbers soar 20 percent from last week. The series is up more than 30 percent vs. its performance just a month ago, when the July 12 episode averaged 3.9 million viewers.

 

Most cable shows tend to lose audience after their season premieres, since cable networks soak so much promotional effort into hyping launches.

 

Even network shows tend to premiere big then fall off a bit as the season wears on.

The exception to this rule is when a new show catches fire with viewers and starts benefiting from buzz and attention. ABC's "Grey's Anatomy," for example, added viewers during its freshman season.

 

The most famous modern example of a series exploding during its first season, however, is NBC's "ER." After a strong premiere in the fall of 1994, the show kept building steam, setting one Nielsen record after another as it pushed past the fable 40-share mark.

 

"Blood's" audience is nowhere near that of "ER's," of course, but the show's stunning ratings spike indicates it may be poised to move from cult hit status to genuine pop culture phenom.

 

Of course, "Blood" still has a ways to go before it matches HBO's signature series, "The Sopranos." At that show's apex, viewer tallies of 11 or 12 million weren't uncommon.

 

HBO might argue that "Blood" is already coming close, however, when you count replays of the series, DVR viewings and on-demand views. Add up all those platforms, and HBO says "Blood" is averaging 11.6 million viewers this season.