ATLANTA — This winter's flu season has reached the epidemic stage, with a key indicator--a deaths-from-flu index--at its highest level in at least eight years, researchers with the Centers for Disease Control said Thursday.
Eighteen states are reporting "widespread" flu problems, and 17 more, including California, are reporting "regional" outbreaks, the CDC said.
To judge the severity of a flu season, CDC researchers track how many deaths are attributable to influenza or pneumonia.
Last week, 7.6% of 15,090 deaths reported to the CDC from 121 major cities were blamed on flu or pneumonia, and that "significantly exceeds" expected levels for the second straight week, said Dr. Walter Gunn, a CDC viral disease specialist.
"This qualifies in our definition as an epidemic," Gunn said, adding that the 7.6% mark is the worst weekly mark in records dating back to the winter of 1981-82. The CDC's epidemic definition is a ratio of 6.7% of deaths or above.
"This confirms our earlier concerns that this would be a worse-than-average year," Gunn said. CDC researchers feared a serious flu season when case reports started coming in last fall several weeks earlier than usual, he said.
Most of the flu cases reported to the CDC this winter have been the type which researchers call A-H3N2. That was the predominant type in the 1984-85 flu season, when an estimated 57,000 Americans died from flu--37,000 more than in the typical winter, Gunn said.
"As far as how many people will die" this flu season, "that depends on how long this peak is sustained," Gunn said. "With any luck, it will come right back down."
Last week, 18 states--up from 10 the week before--reported what the CDC terms "widespread" flu activity: outbreaks of flu or flu-like illness in counties combining for more than half of a state's population.