DENVER -- Doctors say the “worried well,” -- patients who fear they have swine flu, but have little or no symptoms -- are swamping them with phone calls and dropping into urgent care clinics for flu tests.

Guardian Urgent Care in Denver has seen a 20 percent spike in patient visits in the past few days.

“I think it’s fear of the unknown that’s really bringing people in,” said Guardian Urgent Care owner Dr. Rafer Leach. “We have definitely seen a lot of people with very mild illnesses that they might have been able to exclude whether they needed to come in or not just by reading the CDC Web site.”

At some clinics, the demand for flu tests is so great that the swabs used to test for swine flu are in short supply.

“Under normal circumstances we would take three swabs, but because there is a shortage of those swabs, we just take one swab,” said Dr. David Bright, who works at AfterOurs Urgent Care in downtown Denver. Bright said if the first swab tests positive for swine flu, doctors will use the remaining two swabs and send the culture to the health department.

The heightened concern is also evident at the Rocky Mountain Poison and Drug Center. Call volume has spiked, from about 100 calls a day last week, to 600 calls a day this week.

“People want to know what the symptoms of the swine flu are,” said poison center research director, Gregory Bogdan.

Doctors said the symptoms are far more serious than just a minor cough or sore throat. Along with typical cold symptoms, swine flu victims would experience a high fever of 104 degrees Fahrenheit or higher and vomiting and diarrhea.

Even with the swine flu virus spreading and five suspected cases in Colorado, doctors said the likelihood of getting the virus remains, for the time being, low.

“It's a cause for alertness, but it's not a cause for panic at all,” said Bright. “Your chances are far, far greater of just being in an auto accident.”

Doctors said they are not trying to downplay the seriousness of swine flu, because diagnosing the illness in Colorado will depend on people being aware enough of it to recognize and report it.

Leach said he simply wants people to use the Centers for Disease Control as a resource to learn as much as they can about the symptoms of swine flu.

“I don't want to discourage anybody from coming in because it's not really their job to figure this out. It's our job to help them,” said Leach. “But they need to just educate themselves.”