More than 50 Minnesotans have been hospitalized for influenza in the past two weeks, signaling that the state’s flu season has begun in earnest and prompting state health officials to encourage residents to get vaccinated if they haven’t already.

Medical clinics across the state also reported an uptick in flu cases, and the state Health Department on Thursday upgraded flu from “local” to “regional” in its statewide weekly tracking report.

Flu season, which began three months ago, can last through April, meaning that people who are not vaccinated will be susceptible to the nasty virus for several more months. In addition to protecting individuals who get vaccinated, flu shots can help contain the wider spread of the illness, health officials noted.

“The more people who are vaccinated, the more protection we’ll have in the community, especially [for] those at high risk for complications from flu,” said Kris Ehresmann, infectious disease director at the state Health Department.

Flu symptoms include fever, fatigue, body aches, sore throat and coughing, and can emerge suddenly. Most cases are mild, but flu can be serious and even fatal, especially among infants, pregnant women, people over 65, and those with chronic diseases such as asthma and diabetes.

This year’s flu strain is one that has been particularly problematic for the elderly in previous years, because their immune systems may not be able to fight the infection effectively. Nevertheless, the flu attacks all ages, so state officials recommend a flu shot for anyone over the age of six months.

The number of flu-related hospitalizations in the current season, while relatively low, is slightly ahead of last year, when the season didn’t peak until mid-March.

The number of flu cases nationwide is also increasing, so state health officials expect Minnesota’s numbers to increase over the next few weeks.

More information on the disease and locations of flu shot clinics are available on the health department’s website at mdhflu.com.