A surge in school absenteeism suggests swine flu is widespread across Minnesota, meaning it has been reported in half of the state’s regions.

More than 30 Minnesota schools and dozens of clinics have reported a sharp rise in flu-like illness, signaling that swine flu is apparently spreading widely across the state, health officials said Wednesday. 

Based on the reports, Minnesota was bumped up to the highest level of flu activity by the U.S. Centers of Disease Control and Prevention. As of Wednesday, the virus is listed as “widespread,” meaning that flu-like illness has been reported in half of the state’s regions. 

The surge had been expected once school started, and most of the outbreaks have been in the metro area and southern half of the state, “although it’s moving,” said assistant health commissioner John Linc Stine.

The new cases appear to be similar in severity as the first wave of the pandemic, which began in April, Stine said.

While most cases are relatively mild, about eight people have been hospitalized in the past week, he said. 

The pandemic flu virus, also known as H1N1, may not be causing all the illness, but it’s likely playing a “significant role in the upsurge,” the Health Department said in a prepared statement.

As of Monday, only a handful of schools had reported a spike in flu-like illness, but that jumped to more than 30 by Wednesday, Stine said. Schools have been asked to notify the Health Department if more than 5 percent of students are out with flu-like symptoms, or if three or more children in the same elementary class fall ill. 

The state does not try to track every case of the novel flu. But it does receive reports from hospitals and 27 individual clinics, known as “sentinel” sites, as a way of monitoring the spread of the illness. 

“We have been anticipating a possible second wave of this illness,” said Dr. Sanne Magnan, the state health commissioner. “We strongly suspect that may be starting to happen now.”