U.S. health officials say swine flu could strike up to 40 percent of Americans over the next two years and as many as several hundred thousand could die if a vaccine campaign and other measures aren’t successful.
Those estimates from the Centers for Disease Control and Prevention mean about twice the number of people who usually get sick in a normal flu season would be struck by swine flu. Officials said those projections would drop if a new vaccine is ready and widely available, as U.S. officials expect.
The U.S. may have as many as 160 million doses of swine flu vaccine available sometime in October, and U.S. tests of the new vaccine are to start shortly, federal officials said this week.
The infection estimates are based on a flu pandemic from 1957, which killed nearly 70,000 in the United States but was not as severe as the infamous Spanish flu pandemic of 1918-19. But influenza is notoriously hard to predict.

The number of deaths and illnesses would drop if the pandemic peters out or if efforts to slow its spread are successful, said CDC spokesman Tom Skinner, the Associated Press is reporting.