There's no mistaking the feeling most describe as, "Being hit by a mack truck." You've got the flu.

Coughing, headache, fever, chills, upset stomach... chances are you've got H1N1, the most prevalent form of flu this season.

Certain symptoms could mean a trip to the doctor is in store: When patients have an extremely high fever, and...

"Those who develop severe pain the chest, severe vomiting and dehydration, shortness of breath, or for little children those who are very somnolent, can't be aroused or those who are hyper irritable," Dr. Roger Ray, the Chief Medical Officer of Carolina's Healthcare System, said.

For most flu sufferers plenty of fluids, rest, and over-the-counter medication should provide relief, after five to seven days.

But some patients may need more treatment.

"Typically those would be the ones who began getting well and got sick again. That could be another infection taking over," Dr. Ray said.

Experts say the best defense against swine flu is a good offense: The vaccine.

But shot shortages are slowing the vaccine roll-out, so in the meantime, experts say "wash" while you wait.

"It's droplet transmission. If a droplet of the flu lands on my finger and I go and touch my mouth, my nose or my eyes, that's how I'm going to get sick," Dr. Tom Zweng, of Presbyterian Healthcare, said.

Dr. Tom Zweng developed H1N1 response plans for Presbyterian Hospital in Charlotte, North Carolina.

He says hand hygiene is important, because you could be around someone who doesn't know they're sick yet.

"People can be contagious but not displaying symptoms for anywhere from 24 to 48 hours prior to the onset of the typical symptoms," Dr. Zweng said.

It may be the same advice you've heard several times this year -- but it's still the best doctors can recommend.