Flu strain that historically hits elderly, children hard is back in Minnesota

A influenza strain with a history of hitting the elderly and children hard has returned to Minnesota, where 35 schools have reported outbreaks and at least one switched to online learning this week after 1 in 5 students turned up sick.

Cleaners at the Math and Science Academy in Woodbury were spraying disinfectant in classrooms on Wednesday after an outbreak swept through the charter school. The influenza virus primarily spreads through airborne transmission, rather than contact with contaminated surfaces, but school director Kate Hinton said she wasn’t taking chances after seeing illness knock out 145 of her 700 students.

“It never hurts to do a deep clean anyway,” said Hinton, who ordered a switch to remote learning for three days and the cancellation of Friday’s Dorkathalon student celebration. In-person classes will resume after the holiday break.

Lab testing has found the H3N2 influenza strain in the majority of confirmed flu cases in Minnesota so far this season, according to Thursday’s weekly state surveillance update. The state also reported three influenza deaths, with none among children, and 558 hospitalizations.

The infectious disease typically causes high fevers and cold and respiratory symptoms and increases the risk for complications such as pneumonia that can be fatal for the elderly or other high-risk populations.

An uptick is not surprising in mid-December, because Thanksgiving gatherings present an opportunity for the influenza virus to spread among friends and relatives who then carry it back to offices and schools. Even so, the number of hospitalizations in Minnesota doubles the total at this stage of the flu season last year.

The Minnesota Department of Health (MDH) on Thursday urged flu shots for people 6 months and older to offer protection during upcoming holiday gatherings.

“The only thing worse than getting flu is getting flu twice in one year,” she said.

A two-week head start to the flu season, compared with last year, may have caught people off-guard, said Dr. Chase Shutak, medical director of Children’s Minnesota’s primary care clinic in Minneapolis. The pediatric provider reported a sharp increase in flu cases in its clinics and emergency rooms last week, and that 35% of its flu tests turned up positive.

Tamiflu is prescribed for all flu patients 2 and younger and prioritized for others who show up within 48 hours of their symptoms, when the medication works best, he added.

“The classic way that flu presents is like getting hit by a truck,” Shutak said. “You suddenly have a really high fever, everything hurts, you’re exhausted.”

H3N2 was the dominant strain in the winter of 2014-15, when Minnesota reported more than 700 school outbreaks and 10 deaths of children related to influenza. That is the highest pediatric death total for any flu season since at least 2010. The strain also was dominant in 2017-18, when there were six pediatric deaths, and in 2022-23, when there were two deaths.

The 370 flu-related deaths in Minnesota last year, including six pediatric deaths, were likely because of declining vaccination rates and the fact that flu activity was somewhat suppressed during the COVID-19 pandemic, McMahon said. People hadn’t been exposed to the flu virus in several years and may have been more susceptible to infections.

Less than 29% of Minnesotans are up to date with influenza vaccines this season, but that protection rate reaches nearly 60% among senior citizens at greatest risk of complications from infection. The vaccination rate drops under 25% for children nine and younger.

Twenty-nine of Minnesota’s 35 school outbreaks were reported in the past week. Outbreaks are reported when schools are missing 10% of their students because of respiratory illnesses, which could include influenza or other diseases.

H3 seasons typically feature illness waves with dramatic increases but short peaks. State health leaders said they are hoping the current wave follows that historical trend and resolves quickly.

Wisconsin on Thursday reported its first pediatric deaths associated with respiratory illnesses, one resulting from COVID-19 and the other from influenza.