(USA Today) -- The nation's epidemic of new H1N1 flu may have peaked except in New York, New Jersey and New England, a leading federal health expert said Tuesday.

"In the country as a whole, influenza is starting to decrease," says Ann Schuchat of the Centers for Disease Control and Prevention.

The agency has tallied 6,764 confirmed or probable cases and 10 deaths nationwide, Schuchat says, more than half of the global total of 12,954 cases reported Tuesday by the World Health Organization. Laboratory testing indicates that the new H1N1 virus -- commonly referred to as swine flu -- accounts for almost all of the flu virus now circulating nationwide.

Federal health officials haven't dismissed the possibility that the worst is yet to come. Far from it, Schuchat says, noting that the horrific 1918 flu epidemic, which killed 20 million people in the United States alone, was preceded by a mild "herald" wave of cases in the spring, followed by devastating waves of illness in the fall.

"That 1918 experience is in our minds," Schuchat says.

With the flu now apparently in decline in North America, the CDC has begun negotiations with the Pan American Health Organization and health ministries in Latin America and other Southern Hemisphere countries to monitor the ebb and flow of the virus during their winter flu season, which usually peaks in June or July.

The flu's behavior in the Southern Hemisphere over the next few weeks may govern whether a vaccine is necessary, says WHO's Keiji Fukuda.

The CDC and WHO already are gearing up to produce a vaccine to combat the new virus.

Last week, Health and Human Services Secretary Kathleen Sebelius said the government has set aside $1 billion to accelerate vaccine development. HHS spokesman Bill Hall said Tuesday that agency officials have signed contracts worth $660.5 million with three companies to produce crucial components of the vaccine.

Novartis will receive $289 million and GlaxoSmithKline will get $181 million to produce the vaccine's active ingredient, made of a component of the virus, and a booster in case the active ingredient isn't potent enough. Sanofi-Aventis will receive $190.6 million to produce the active ingredient only.

In addition, those companies, MedImmune and CSL Biotherapies of Melbourne, Australia, will receive $150 million to develop prototype lots of vaccine and to carry out preliminary tests.

The rest of the money will be used to purchase more vaccine ingredients, Hall says.

(c) USA TODAY