UPDATE 3-Obama declares swine flu a national emergency

* Disaster proclamation intended as proactive measure

* CDC said swine flu widespread in 46 of 50 states (Adds details on new antiviral drug)

By Patricia Zengerle

WASHINGTON, Oct 24 (Reuters) - U.S. President Barack Obama has declared 2009 H1N1 swine flu a national emergency, the White House said on Saturday.

The declaration will make it easier for U.S. medical facilities to handle a surge in flu patients by allowing the waiver of some requirements of Medicare, Medicaid and other federal health insurance programs as needed, the White House said in a statement.

The U.S. Centers for Disease Control and Prevention said on Friday that swine flu has become widespread in 46 of the 50 U.S. states, a level comparable to the peak of ordinary flu seasons but far earlier and with more waves of infection expected.

Obama signed the statement on Friday night.

The White House statement said the declaration was intended to prepare the country in case of "a rapid increase in illness that may overburden health care resources." It was similar to disaster declarations issued before hurricanes hit coastal areas.

"It's important to note that this is a proactive measure -- not a response to a new development," an administration official said.

"H1N1 is moving rapidly, as expected. By the time regions or healthcare systems recognize they are becoming overburdened, they need to implement disaster plans quickly," he said.

Seasonal flu normally peaks sometime between late November and early March and kills about 36,000 Americans in an average year.

Swine flu has hit young adults and children the hardest, while seasonal flu normally is more dangerous for people over age 65.

H1N1, declared a public health emergency earlier in the year, has killed more than 1,000 people in the United States and put more than 20,000 in the hospital since it emerged earlier this year, the CDC said. But health officials are quick to note that the actual number of cases cannot be measured.

The new declaration clears the way for waivers of federal requirements that, for example, could prevent hospitals from establishing off-site, alternate care facilities that could help them deal with emergency department demands, the White House said.

The Health and Human Services Department is trying to deliver vaccines against H1N1 but says production is falling short of projections because companies are having trouble making them.

HHS has also moved to make available stockpiles of antiviral drugs oseltamivir, made by Roche AG (ROG.VX) under the brand name Tamiflu, and zanamivir, an inhaled drug made by GlaxoSmithKline (GSK.L) under the brand name Relenza.