Flu-like illnesses caused 167 outbreaks in Minnesota schools last week, making this season the worst for schoolchildren in five years.

With most classes dismissed this week for the holiday break, the next front for the flu’s spread is likely to be at home or at community events, but the dominant flu strain this season is one that tends to affect children the most.

The number of school outbreaks jumped from 60 in the previous week, according to the weekly flu update provided by the Minnesota Health Department on Thursday.

By comparison, there was just one outbreak in long-term care facilities last week, making it one of only eight reported so far this season.

Minnesota has not seen so many school outbreaks since the 2014-2015 season, when nearly 300 schools reported that at least 5% of their students or three or more students in one elementary class had called in sick around this time of the year.

That means there are a lot of sick children, but because the definition of a flu-like illness is broad and many cases are not confirmed by a laboratory, some of those affected could be showing symptoms of cold viruses, which are also common this time of year.

Flu symptoms typically develop abruptly, according to the Centers for Disease Control and Prevention, and often include a fever and body aches, which are less prevalent with the common cold.

Those and other symptoms, such as head congestion, coughing, sore throat and sneezing, are sending many people to the doctor, with 6.5% of clinic visits caused by flu-like illnesses, up from 3.4% in the previous week.

This flu season is unusual in that most laboratory-confirmed cases are of the B strain of the flu virus, which typically does not appear in large numbers until late spring as the season winds down.

Were it not for the school outbreaks and the many clinic visits, this influenza season would otherwise be called mild.

Compared to the past five seasons, the number of people hospitalized with the flu is at the low end, with 78 people becoming inpatients last week, compared to 70 the previous week and 351 for the season. So far, there have been seven deaths caused by the flu, none of them children.

Still, most hospitals have put visiting restrictions in place to prevent the spread of flu to their most vulnerable patients.

Each hospital has its own policy, but typically those with symptoms as well as young children are asked to refrain from visiting.

While the holiday season is a time for gatherings, it also presents an opportunity for the flu virus to spread.

A person can become infected by inhaling droplets in the air that are made when an infected person coughs, sneezes or even talks.

Flu can also be spread by touching infected surfaces.

The flu virus is also being imported to the state as people travel to Minnesota from other parts of the country.

Every state has been affected, with states in the southern United States reporting the highest activity.