By Jenn Bernstein

ALLENTOWN, Pa. (CBS) — Flu season is upon us and this year it’s not something to be taken lightly.

The Center for Disease Control and Prevention says influenza cases continue to increase throughout the country, and that most parts, including Pennsylvania, are experiencing high levels of influenza-like-symptoms.

READ: Seasonal Flu Resource Guide

Medical officials say 2010 and 2011 were considered mild years, but the number of doctor and emergency room visits are already showing a much more aggressive sickness this year.

Lehigh Valley Hospital has set up a tent outside its emergency room to efficiently and safely see and treat an influx of flu patients, to reduce its spread in the hospital.

Terry Burger, the hospital’s Director of Infectious Diseases, says they’ve seen a steady increase in flu-like symptoms since the first week of December.

“The flu’s hit early and it is hitting hard,” said Burger. “We’re heading into a long protracted severe flu season.”

Flu symptoms include fever, chills, headache, fatigue, sore throat, cough and a stuffy nose.

“We are seeing some very sick people, all the more reason to get people vaccinated,” said Burger.

The outside heated tent opens at 11 a.m. Tuesday.