AUGUSTA – Several cases of influenza, including one flu-related death, have been confirmed in Maine this season in laboratory tests, health officials said Tuesday.

The cases were found in Penobscot, Piscataquis and Franklin counties, said Dr. Dora Anne Mills, director of the Maine Center for Disease Control and Prevention.

The flu was detected in a young adult who died in Penobscot County the week before Christmas, Mills said. The victim was visiting Maine from the Southeast, where flu activity has been prevalent.

“Flu season has arrived,” Mills said. “There’s probably more influenza out there, but not everybody in the hospital gets tested.”

The flu is a contagious respiratory illness caused by influenza viruses. It can cause mild to severe illness, and at times can lead to death.

Flu viruses spread mainly from person to person through coughing or sneezing. Each year, more than 200,000 people are hospitalized with flu complications and about 36,000 people die, according to the federal Centers for Disease Control and Prevention.

Nationally, influenza activity increased the week before Christmas, according to the CDC. Maine was among 25 states reporting sporadic flu activity; four states – Alabama, Florida, Georgia and Mississippi – reported widespread activity.

Vermont was the only state to report no cases of the flu. New Hampshire reported sporadic flu activity.

People can take preventive measures against the flu by using good hygiene and getting flu shots, Mills said.

“With the reopening of schools and many returning to work this week, it is especially important that we all heed the three basic guidelines of covering coughs and sneezes, washing hands frequently and staying home if we’re ill, particularly with a fever,” she said.

Even though flu season has started, Mills said it’s not too late to get a flu shot, especially for high-risk groups that include children ages 6 months to 6 years, people 50 and older, pregnant women and those with chronic medical conditions such as diabetes and heart disease.

The seasonal flu is unrelated to the avian flu virus, which is found chiefly in birds, Mills said. Thousand of birds have been tested in the U.S. and Canada – including more than 1,000 in Maine – but none have tested positive for avian flu.