FILE - In a Jan. 9, 2013 file photo, four-year-old Gabriella Diaz sits as registered nurse Charlene Luxcin, right, administers a flu shot at the Whittier Street Health Center in Boston, Mass. The Centers for Disease Control and Prevention on Monday, Jan. 5, 2014, reported flu season is getting worse. Flu was widespread in 43 states and flu activity was intense in most of them, according to the latest national data for the week of Christmas. (AP Photo/Charles Krupa, File)

NEW YORK, N.Y. - The flu is now widespread in all but seven states, and hospitalization rates match the dismal season two years ago. While health officials fear this will be an unusually bad year, it's too soon to say.

The latest figures released Monday by the Centers for Disease Control and Prevention show the flu hitting hard in most of the 43 states where the illness was widespread. But the flu was not yet rampant in populous states like California and New York.

The report is for the week of Christmas, and it shows the flu season following a similar track as the last two, when flu activity peaked no later than mid-January. Perhaps that will happen this winter, too, the CDC's Dr. Michael Jhung said.

HOW BAD IS THIS FLU SEASON?

It's not clear yet. Experts are worried because the nasty bug that's making most people sick isn't included in this year's vaccine. Preliminary data on how well the vaccine is working is still weeks away. Among infectious diseases, flu is considered one of the nation's leading causes of death, killing roughly 24,000 a year, on average.

HOW UNUSUAL IS FLU THIS YEAR?

The different flu strain makes predictions more difficult. The current season hit hard in December — earlier than usual. But the last two flu seasons hit early, too. So far, flu hospitalization rates are similar to the harsh season two years ago, which was dominated by a similar flu virus. Especially this year, health officials this year are urging doctors to treat flu patients promptly with antiviral medications.

HAS FLU BECOME EPIDEMIC?

Yes, but that's not unusual. "It's safe to say we have a flu epidemic every year," Jhung said Monday. Epidemics occur when a virus spreads quickly and affects many people at the same time. According to one CDC definition, flu is epidemic when a certain percentage of deaths in a given week are due to flu and pneumonia. By that measure, flu epidemics occurred in nine of the last dozen winters, including this one. Flu-related deaths surpassed the epidemic threshold three weeks ago, then dropped below that level the next week. But other measures indicate flu still is epidemic.

IS IT TOO LATE TO GET A FLU SHOT?

CDC officials say no. Even if the flu season peaks soon, it will still be around for months. Despite the new flu strain, the vaccine has been well matched in roughly a third of the flu cases seen so far. And it is considered to be effective against some other flu viruses that could surge in the late winter or spring. About 40 per cent of the public was vaccinated against flu as of November, which is about normal in recent years, Jhung said.

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Online:

CDC flu update: http://www.cdc.gov/flu/weekly/

News from © The Associated Press, 2015