Allina Health will restrict visitor access at its hospitals starting Tuesday to reduce the risk of vulnerable patients catching the flu after an announcement by state health officials that the virus is active across much of Minnesota.

The precautionary step occurs whenever the Minnesota Health Department declares that influenza is widespread across the state, said Allina spokesman Tim Burke. The department made that announcement late last week as part of its weekly tracking of the flu, which so far has been relatively mild in Minnesota.

Allina officials are asking that people who are ill and children younger than 5 refrain from visiting patients at its 13 hospitals. Visitors with sore throats or coughs should wear masks to prevent the spread of germs.

The Health Department has reported 329 flu-related hospitalizations in Minnesota as of Jan. 21 — a relatively low number compared to prior seasons. No flu deaths in children have been reported so far this year.

However, the prevalence of influenza increased last week among samples tested by a state surveillance network of 310 clinic and hospital-based laboratories across the state.