The flu is beginning to show up in force in St. Paul and Rosemount-Apple Valley-Eagan elementary schools. And within the past week, it has moved from geographically “regional” to “widespread” across Minnesota.

Minnesota Health Department epidemiologist Melissa McMahon said Thursday that so far most of it appears to be a strain called H3 Influenza A, which often leads to a worse illness than other strains.

Overall, this year’s flu shot is not expected to offer good protection against the worst strain, but it can be helpful with other strains and with lessening the severity of the illness, she said.

“We tend to see more hospitalizations and death, and that tends to be for people age 65 and older,” McMahon said. “We really want those guys to go into their doctors if they feel ill.”

Doctors can prescribe antiviral medication, said Health Department epidemiologist Karen Martin, which can be especially helpful for people most at risk: those with asthma, the very young and very old, and pregnant women.

The department encourages doctors not to depend entirely on flu tests given in the office but to rely on their own judgment when making a diagnosis, Martin said. The rapid office tests have a problem with false negatives, showing that some patients don’t have the flu when in fact they do, she said.

Cases of the flu must be reported to the state Health Department once 5 percent or more of a school’s students are absent because of flu-like systems — or when three or more children are missing from a single classroom in elementary schools. That has happened in 10 of 38 St. Paul elementary schools. In the Rosemount-Apple Valley-Eagan district, six of 18 elementary schools have reached the 5 percent mark, said Joan Bertelsen, health services coordinator; among older students, she said, there has been an uptick in flu cases as well.

In the White Bear Lake Area schools, none has yet met the 5 percent threshold, spokeswoman Marisa Vette said. The same is true in the North St. Paul-Maplewood-Oakdale district, spokesman Cory McIntyre said. If the district reports to the health department, parents will be notified and receive information.

So far this fall, one Minnesota child has died of the flu, and the death of a student in Owatonna, Minn., is being investigated as possibly flu-related.

For a description of flu symptoms and recommendations on when to get medical help, go to the Health Department’s website at bit.ly/ 12SBqpS.

Debra O’Connor can be reached at 651-228-5453. Follow her at twitter.com/DebOConnorPP.