After last year's mildest flu season on record, influenza has returned with a vengeance.

A "moderately severe outbreak" of "old-fashioned influenza" is filling emergency rooms across the region and the country.

According to Dr. William Schaffner, Chair of the Department of Preventative Medicine at Vanderbilt University, this year's influenza outbreak began on the East Coast early this year, in November, and quickly spread westward.

The Philadelphia region, along with other East Coast metropolitan areas, "is having a harder time" with the flu than many other parts of the country, Schaffner said in an interview with the Huffington Post.

At Lehigh Valley Hospital, medical officials opened a "flu tent" outside the emergency room to handle the overflow. 

"If you haven't been vaccinated, still get vaccinated," Schaffner said. "If you haven't gotten it, wash your hands and keep your distance from people who are coughing and sneezing. Instead of going to the movies, rent a movie and watch it at home."

Watch the video to learn more.

The best defense against contracting the flu is a flu shot and strict attention to preventive measures such as handwashing and avoiding crowds.

Though Montgomery County officials on Friday announced that they were increasing the hours of availability for free flu vaccinations at locations in Norristown, Pottstown, and Willow Grove, Bucks County has made no similar moves.

In fact, finding a flu shot now might be tougher than it was in September or October, according to the Centers for Disease Control and Prevention.

"You may need to contact more than one provider (pharmacy, health department, or doctor) to find available vaccine," the CDC said in an update on the country's bout with the flu.

According to the Pennsylvania Department of Health, most of the flu viruses circulating this year are the A/H3N2 variety, "a strain that generally causes severe illness in older age groups."

Those strains are similar to the strains included in this year's flu vaccine, the department said. So far this season, at least 971 people in Pennsylvania have been hospitalized for the flu; the median age of those admitted has been 67. As of Wednesday, at least 22 people had died.

Because flu activity doesn't typically peak until mid-January to February, the CDC warns that that flu activity is likely to continue for weeks, and advises that flu shots taken now still will offer some protection against the illness.