FRANKFORT, Ky. — Kentucky's health commissioner said Monday he expects the Kentucky Derby to go on as scheduled, despite concerns about the spread of swine flu.

"Since the nature of this virus is so unpredictable, I have to leave enough open room to say I can't guarantee that," said Dr. William Hacker. "It's our assumptions that the derby will continue as planned and be successful."

Hacker said he has informed the Centers for Disease Control and Prevention that the derby will bring "a surge of individuals from around the world."

No cases have been confirmed in Kentucky, but the derby is expected to draw some 300,000 people to Kentucky, most of whom will be in shoulder-to-shoulder contact at Churchill Downs in Louisville.

Hacker said health officials will continue to monitor the number and severity of cases leading up to the Kentucky Derby. "But before we have any discussions that would affect derby plans, certainly I have no information today that makes me want to do that."

The World Health Organization says there are now 40 confirmed cases of swine flu in the United States and it is "very concerned" about the disease's spread.

None of the cases in the U.S. have been fatal. In Mexico, the suspected death toll has reached 149 people. Of those, 20 have been confirmed as swine flu. Public events have been canceled in that country and surgical masks are being given to subway passengers in Mexico City.

In the U.S., the Obama administration declared a public health emergency and began sending roughly 12 million doses of Tamiflu from the federal stockpile to the states. Some schools closed in New York City, Texas, California, South Carolina and Ohio because of concerns about the spread of swine flu.

Hacker said Kentucky has asked the federal government for antiviral drugs — enough to treat hundreds of thousands of people — just in case they're needed.

Gov. Steve Beshear said Kentucky has been preparing for pandemic flu for years, allowing a quick reaction to a potential swine flu outbreak in the state.

"That preparation is allowing us to quickly coordinate the appropriate response to protect Kentuckians," Beshear said.