WebMD is apparently the target of yet another merger by 2 major health web sites. Last week, Revolution Health and Everyday Health merged.
This week, HealthGrades.com has announced its acquisition of WrongDiagnosis.com.
Here's a Compete.com snapshot at how the 5 sites stack up against each other.
It looks like Revolution and Everyday are in better position to take on WebMD. HealthGrades has a ton of content behind a premium content wall.
But all of them, including WebMD, have a long way to go in catching Yahoo's Health site:
UPDATE: As a commenter pointed out, Compete can only measure the Yahoo.com traffic. So, I looked up the most recent comScore ratings for the health niche. Here they are, showing WebMD as the clear leader: