U.S. health officials say swine flu activity is dying down a bit, but the number of cases has surpassed 37,000 and deaths hit 211.

The numbers rose from 170 deaths and nearly 34,000 confirmed and suspected swine flu cases reported last week.

Officials believe those cases — which sought treatment and underwent testing — are just the tip of the iceberg. They estimate more than 1 million Americans have been infected with the virus, though many probably had only mild illness.

Swine flu is the predominant flu type circulating currently, with nine states reporting widespread cases