ATLANTA (NBC News) – The Centers for Disease Control reports 46 states have widespread flu activity, compared to just 12 states at this time last year.

Emergency room doctors in Escondido, California have set up a special tent outside the hospital to handle a surge in flu patients.

The last time they needed an extended treatment area was during the 2009 flu pandemic.

So far 41,000 cases have been confirmed nationwide.

The flu can be deadly, especially for those with underlying health conditions.

The flu vaccine is not as effective this year, but experts say some protection is better than none.

“Even if you get sick having had the vaccine, your illness tends to be milder not quite as severe,” says Vanderbilt University Medical Center’s Dr. William Schaffner.

The vaccine also lessens the chance of getting flu complications like pneumonia.