Feeling lousy for three weeks or more? You may have flu for the second time.Hundreds of Coloradans are complaining of a bug they just can't shake this flu season and it's not their imagination."It feels like this year we're seeing a whole lot more cases," said Dr. Lee Moorer, medical director at Guardian Urgent Care in Denver.Waiting rooms are packed with patients with nasty and violent coughs."Let me tell you, everybody's getting it," Moorer said.Unlike past years, doctors said this year's virus tends to linger longer.Doctors said a typical influenza virus will run its course in 10 to 14 days. But this year, patients such as Laura Levin have been sick for two weeks and are just now coming in for diagnoses and treatment."Usually it only takes a couple of days (to shake it) when I've had it in the past," Levin said.She looked miserable, waiting to see a doctor."(I have) a cough, burning (throat), no voice in the morning. I cough it up at night," Levin said.Doctors have seen it happen too many times this year."And then boom! You get hit with another one. So now you've got another 10 to 14 day kick. That can be a little bit confusing because we start to think -- bacterial infection. However, in the majority of the cases it's just another viral infection," Moorer said.At the Walgreens down the street, TamiFlu sales are strong. The anti-flu, prescription medication is hard to keep on the shelf."Just lately it's really picked up. We've already done probably five (doses) today," said Dawn Lefevre, pharmacy manager at the Broadway store.In fact, she's seeing doctors prescribe TamiFlu for a sick person and for other healthy people in the household to try and slow the outbreak down.The Centers for Disease Control and Prevention reports the flu season is already the worst since 2004.Flu and pneumonia-related deaths were recently measured at epidemic levels nationwide, according to the CDC. The CDC had also admitted the flu vaccine isn't as effective as usual.