Frieden has made national headlines in a bid to get New Yorkers to live a healthier lifestyle — with bans on smoking in a city known for smoky clubs and cigar-fueled power lunches, and on certain fats in restaurant foods.

But he's also a well-known infectious disease expert who will inherit a looming decision on how best to manage the swine flu outbreak — including whether or how to produce a vaccine.

"I am honored and humbled by the challenge and privilege of working with the greatest public health agency in the world," Frieden said in an e-mail to CDC employees Friday morning. Of their round-the-clock work since discovering the new swine flu virus last month, he added: "CDC shone."

The new CDC chief 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," Obama said in a statement announcing Frieden's appointment.

Frieden already has ideas, telling his new staff that science — along with "creative and strategic thinking" — will guide how they ramp up public health programs that in turn play a role in "increased productivity in society, and to reducing costs for America's families, businesses and government."

The White House said Frieden, 48, will begin at the CDC in early June. His appointment does not require Senate confirmation.

Public health advocates welcomed the choice.

"Dr. Frieden is a bold leader who has the courage to shake up the status quo if science and evidence show that change needs to happen," said Jeff Levi of the nonprofit Trust for America's Health.

"He has not backed away from the tough public health challenges and in doing so has helped the people he served lead healthier, longer lives," added Dr. Georges Benjamin of the American Public Health Association.

As the top public health official in the nation's biggest city for seven years, Frieden shook up New York businesses early on as his department banned smoking in almost all workplaces. The move has been credited with reducing the city's number of smokers by 350,000.

Then came the food fight, as fast-food companies all over the country had to change their recipes after Frieden pushed through a ban on heart-damaging trans fats in New York City restaurant food. Many of the same restaurants now also must post the calorie content of their meals right on the menu.

Frieden pushed the actions through by a decree of the city's board of health, meaning he never had to seek input from the city Council or fight industry lobbyists over legislation — quite a different playing field than the federal government. He has been unapologetic for his methods, noting that chronic illnesses like heart disease — fueled by both bad diets and smoking — deserve to be treated with the same seriousness as would an outbreak of a contagious disease.

Nor is he a newcomer to CDC. In the early 1990s, he was part of the agency's famed disease-detective unit, the Epidemiologic Intelligence Service, and spent five years working in India.

"Dr Frieden is a consummate innovator," Dr. Richard Besser, CDC's acting director, told his staff in a Friday e-mail.

Besser had become a well-known face in the past month as he calmly explained the latest details of the swine flu outbreak in daily briefings and frequent TV interviews. Besser had previously led the CDC's terrorism and emergency response office and said he was looking forward to returning there when Frieden takes the helm. CDC's previous director, Dr. Julie Gerberding, resigned in January.

Associated Press Writer David B. Caruso contributed to this report.