PORTLAND, Ore. (KOIN) — Six children and an adult are now sick with E. coli at the Montessori of Alameda preschool in Portland.

The Multnomah County Health Department has been investigating the illness since March 7. All the students were asked to get tested as a precaution.

Chris Duillet just found out his 2-year-old son is one of the children who contracted E. coli. His test results came back positive despite the fact that the boy wasn’t show any of the symptoms.

“He’s fine, he’s got no issues, and that’s why we were caught by surprise, because he’s running around in the house,” Duillet said.

Officials say the kids should be tested even if they don’t have symptoms. Duillet said his doctor gave him test kit for his 7-year-old daughter as well.

Genetic testing of the bacteria shows that some of the cases are confirmed to have the same strain of E. coli that was linked to the recall of I.M. Healthy SoyNut Butter. School officials say they do not serve that product to their kids.

Multnomah County Health Officer Paul Lewis told KOIN 6 News last week that this is the “bad kind” of E coli. It spread through person-to-person contact, not just through food, although that is a common way people get infected.

“This is a nasty bacteria, it can make you very sick and it’s easily spread from person to person,” Lewis said.

It’s the most severe type of Shiga Toxin E. coli. The bacteria produces a toxin which can damage blood vessels, especially in the kidneys.