Flu season has reached Jackson Hole.

About 20 patients have shown up at St. John’s Medical Center Family Health and Urgent Care Clinic in the past few days with confirmed cases of influenza, according to medical director Dr. Jim Little Jr.

There had been no confirmed cases until this week, he said.

The appearance of flu comes at about the usual time of year, though earlier than last winter.

“This is pretty much right on time,” Little said. “Typically, the spike in the flu season starts in December or January. Last year was very late.”

This year’s vaccination formula is effective against the strains that are circulating, Little said.

“The most important thing people can do is get their flu shot,” he said. “It’s not too late.”

Vaccinations usually take up to two weeks to become effective.

The smattering of cases reported in Jackson Hole comes at the same time that the federal Centers for Disease Control and Prevention has increased its assessment of the severity of Wyoming’s flu situation.

In its most recent report, the CDC raised its rating of the state’s outbreak level to “regional” rather than “local.”

The counties hit hardest have been Sheridan, Campbell and Big Horn.

Other health care providers in the Jackson area report slightly less worrisome influenza activity.

Emerg-A-Care has seen only a handful of actual flu cases. Most of the people treated recently for symptoms that might have been flu turned out to have less dangerous upper respiratory infections, Dr. Brent Blue said.

“People feel really sick, but it’s not influenza,” Blue said.

Flu is a virus that attacks through the respiratory system. Symptoms include headache, sore throat, dry cough, fever, muscle aches and stuffy nose.

The outcome can be anything from mild discomfort to death, depending on the particular strain and the strength of the person who contracts the virus.

The people who are most vulnerable are children, the elderly and people already weakened by other illnesses that hurt their immune response.

Teton County Public Health has run out of vaccinations, but some vaccine is still available in the area.

St. John’s Family Health and Urgent Care Clinic, Emerg-A-Care and store pharmacies at Smith’s Food and Drug and Albertsons are still administering shots.

Besides vaccines, commonsense prevention includes frequently washing your hands, covering your mouth when you cough or sneeze, and avoiding close contact with infected people.