The number of H1N1 swine flu cases in the United States has dropped steadily for four weeks as vaccine stockpiles continue to grow, the U.S. Centers for Disease Control and Prevention (CDC) reported Monday afternoon.

"Visits to doctors for influenza-like illness nationally decreased sharply this week over last week with all regions showing declines," announced the Atlanta-based CDC on its website, referring to a preliminary analysis of the week ending on November 21.

"This is the fourth consecutive week of national decreases." According to the update, the number of states reporting undefined "widespread influenza activity" also dropped by 11 during that week; from 43 to 32.

(Read more at Pediatric SuperSite)