ST. LOUIS COUNTY, Mo. — Cover your mouth, wash your hands, it's that time of year again.

Flu cases are spiking across the bi-state and the numbers are in the thousands.

"The flu is really spreading like the plague around here," said Hoech eighth-grade science teacher Amanda Kowalczyk.

This week the Ritenour School District sent a letter home with parents. It's a heads up that the flu is hitting the St. Louis area hard.

"We want to remind parents, you know, if your child doesn't seem healthy to make sure that you take them to the doctor that you see your school nurse," said School District spokesperson Doug Bray.

In St. Louis County, the health department reported more than 3,200 flu cases since January.

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Several of those cases include staff members and students here in the Ritenour School District.

"Really, on a daily basis we want parents to know that we're doing our best every day to keep our kids healthy in our schools," said Bray.

It starts by disinfecting surfaces, an important step Kowalczyk said students need to see to understand.

"This was a visual example, trying to keep the kids more aware of the germs that are around them," Kowalczyk said pointing to a bulletin board of bread slices in bags.

She and her students created the bulletin board titled, "it's cold and flu season."

It uses the bread to show just how germs can spread.

"We took a piece of bread and literally walked down the hallway having the kids touch it collecting all the germs, so we took all of the different samples and put them in the baggies and we are waiting for mold to grow," she said.

While they wait, nurses in the district are working to stop the real thing from spreading.

"Everybody is more concerned with what's in the best interest of all of our students and how we can keep them healthy and in their learning environments," said Ritenour district nurse Erica Whitley.

The Centers for Disease Control estimates about 12,000 people have died from the flu so far this season.

The district is encouraging parents to reach out and speak with a nurse if they aren't sure their child has the flu.