New York City Health Commissioner Dr. Thomas Frieden was chosen by the Obama administration to head the Centers for Disease Control and Prevention Friday.

Mayor Michael Bloomberg described Frieden's appointment as the city's loss and the nation's gain. Frieden, an infectious disease specialist, has been at the helm of the New York City Department of Health since 2002. Over the past seven years, Frieden has led a campaign to reduce the number of smoking New Yorkers by 350,000 and cut teen smoking in half. He also worked to expand cancer screenings, reduced AIDS deaths by 40 percent and cracked down on trans-fats.

In a statement, President Barack Obama said his new CDC director has been "a leader in the fight for health care reform, and his experiences confronting public health challenges in our country and abroad will be essential in this new role."

As the head of the CDC, Frieden will face many difficult decisions, including whether or not to produce a swine flu vaccine. Frieden is expected to take over the federal agency in June. His appointment does not require a Senate confirmation.