AUGUSTA — The first flu cases of the season were detected in Maine early last week, the Maine Center for Disease Control and Prevention announced Friday.

Cases of Influenza A were confirmed in a young adult in Aroostook County, a teenager in Penobscot County and an adult in Cumberland County. None of the patients was vaccinated or required hospitalization.

A long-term care facility in Penobscot County also reported an outbreak of influenza on Oct. 31. Maine’s Health and Environmental Testing Laboratory confirmed Influenza A in an employee and a resident of the facility on Nov. 2.

The Maine CDC recommends getting a yearly flu shot as the best way to protect against the illness for everyone age 6 months and older. The flu vaccine is widely available now through pharmacies, physicians and other sources.

“The flu is still a serious illness in the United States,” said Dr. Sheila Pinette, director of the Maine CDC. “Mainers should do all they can to protect themselves and their loved ones against this illness.”

About 20 percent of U.S. residents get the flu each year, according to the Maine CDC. Symptoms include fever, cough, sore throat, runny or stuffy nose, muscle or body aches, headache and fatigue.

On average, more than 200,000 Americans are hospitalized annually for flu complications. High-risk groups for complications include children younger than 5 and people over 65; pregnant women; Native Americans; people who have underlying medical conditions such as asthma, heart disease and weakened immune systems; and the morbidly obese.

Many pharmacies in Maine offer flu shots without an appointment, including Maine-based Community Pharmacies, which has stores in Gorham, Saco, Cornish and seven other towns. Pharmacists who participate in flu shot clinics are trained to administer vaccines.

“We have plenty of vaccine,” said Joe Bruno, president and CEO of Community Pharmacies. “You can walk into any of our stores and get a flu shot, pretty much without waiting.”

A flu shot typically costs $25 or is free to customers covered by Medicare, Bruno said. Community Pharmacies will bill directly for customers covered by Medicare and Anthem, he said.

Hannaford supermarket pharmacists administered more than 12,000 vaccines last season, and they expect to double that number this season, company spokesman Eric Blom said. Hannaford operates 50 pharmacies in Maine, including in its supermarkets in Portland, South Portland, Westbrook, Gray and Falmouth.

“It’s a service that’s growing fast for us,” Blom said, noting that customers who don’t like needles may opt for a slightly shorter intradermal needle, which increases the cost to $32.99 per shot.

Immunity protection begins about two weeks after vaccination, Pinette said.

In addition to getting a flu shot, Pinette recommended that everyone apply proper health etiquette throughout cold and flu season to prevent germ transmission, including regular hand washing, coughing into the crook of your elbow and staying home when ill.

For questions about the vaccine, call the Maine Immunization Program at 287-3746 or 800-867-4775, or e-mail immuneme@maine.gov.

For questions about the disease or to report cases, call the Infectious Disease Epidemiology Program at 800-821-5821 or e-mail disease.reporting@maine.gov.