The holiday season brings gifts, gatherings and good cheer, but it also can speed up the transmission of the seasonal flu virus.

Over the past several weeks, federal health officials have reported that some Southern states have been the hardest hit and that cases were picking up in several others, including Wisconsin.

Travel to and from the affected regions will spread the flu bug, and Minnesota health officials in the past few weeks have seen several signs that more people are getting sick.

"Certainly getting together with friends and family over the holidays and with people in close confines is probably going to promote the spread of influenza," said Karen Martin, an epidemiologist with the Minnesota Health Department.

The number of Minnesotans hospitalized with flu-like illnesses increased 38 percent in the past week and now stands at 359 for the season, according to the state's flu tracking report released Thursday.

"In the last two weeks it has jumped up significantly," Martin said.

It also hit schools, with 19 new outbreaks reported.

"Luckily those kids are going on break so that will stop the spread in schools, but it is out in the community so there will be transmission going on between family and friends," said Martin.

Although most people refer to it as the flu, there actually are many strains of the virus.

Laboratory tests show that one of the dominant strains this year hits the elderly and young children particularly hard.

"People can develop pneumonia and other respiratory complications from it that will land someone in the hospital, particularly the elderly," Martin said.

Each person can have a different reaction to the virus. If someone had caught the flu previously, they could have full or partial immunity to new flu viruses. Also, the viruses are constantly mutating and changing as they're passed among hosts.

Flu can also cause complications in people with underlying chronic conditions, such as asthma or chronic obstructive pulmonary disease.

The virus is spread through respiratory droplets expelled when an infected person sneezes or coughs. It can also remain on surfaces such as doorknobs or faucet handles.

The best way to prevent contracting the flu is to get vaccinated. The vaccine, a concoction that is designed each year to prevent the most dominant strains that researchers think will spread, is usually only 40 to 60 percent effective because it cannot provide protection against all possible strains.

But those who got the vaccine might see milder cases if flu infection does occur.

Still, the Centers for Disease Control and Prevention in Atlanta estimate that only about 39 percent of the population was vaccinated as of last month. The vaccine is generally recommended for anyone over the age of 6 months. Like last year, the vaccine is only offered in the form of shots. The nasal spray vaccine is not recommended.

Flu symptoms include fever, chills, muscle aches, cough, congestion, runny nose, headaches and fatigue.

While holiday activity could jump-start the number of flu cases seen in the state, new infections will continue well into the spring.

"We are going to see influenza through May," said Martin. "It is a long season."