(NBC) -- Flooded emergency rooms, canceled school events and rumors of a Tamiflu shortage are all signs the United States is experiencing one of the worst flu seasons in decades.

Boston's mayor has declared a state of emergency in the wake of 700 confirmed cases.

The city will provide free flu shots this weekend.

Lehigh Valley Hospital near Allentown, Pennsylvania set up a tent outside the emergency room to triage flu patients.

"If they've got mild illness, we can see them, evaluate, them treat them if needed and discharge right from the tent," says Lehigh's Terry Bulger.

Doctors at the Mayo Clinic in Rochester, Minnesota are seeing more patients than they did during the peak of the H1N1 epidemic.

They are implementing visitor restrictions at all 15 of their hospitals.

Even sunny south Florida has seen a surge in cases.

While a majority of patients will eventually recover, there have been deaths, most recently, 6-year-old Tahila Johnson from Garland, Texas.

"She was a Daddy's girl, like I don't know what to do, it's like my heart is gone now," her father says.

Health officials say the flu vaccine is a good match for the strain circulating this year and it is not too late to get a shot.

Tamiflu, one of the only drugs used to treat the flu, is in short supply in many pharmacies.

The manufacturer usually increases production in January and February, but because the flu hit early this year most of the available drug has been used.