ATLANTA — In a disturbing new projection, health officials say up to 40 percent of U.S. residents could get swine flu this year and next and several hundred thousand could die without a successful vaccine campaign and other measures.
The estimates by the Centers for Disease Control and Prevention are roughly twice the number of those who catch flu in a normal season and add greater weight to hurried efforts to get a new vaccine ready for the fall flu season.
Swine flu has hit the United States harder than any other nation, but it has struck something of a glancing blow. The virus has killed about 300 U.S. residents and experts believe it has sickened more than 1 million, comparable to a seasonal flu.
Health officials say flu cases may explode in the fall, when schools open and become germ factories.
A world health official said the first vaccines are expected in September and October. The United States expects to begin testing on volunteers in August, with 160 million doses ready in October.
The 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 Spanish flu pandemic of 1918-19. Deaths and illnesses from the new virus would drop if the pandemic peters out or if efforts to slow its spread are successful, said CDC spokesman Tom Skinner.
Besides pushing flu shots, health officials might urge measures such as avoiding crowded places, hand washing, cough covering and timely use of medicines such as Tamiflu.
Because so many more people are expected to catch the new flu, the number of deaths over two years could range from 90,000 to several hundred thousand, the CDC calculated. Again, that is if a new vaccine and other efforts fail.
In a normal flu season, about 36,000 people die from flu and its complications, according to the American Medical Association.
The World Health Organization said as many as 2 billion people could become infected in the next two years, nearly a third of the world population.
A two-year period is used because past flu pandemics have occurred in waves over more than one year.