Jessica Grose of The New York Times writes that “two days before my 37th birthday, I received the following bone-chilling email from my daughter’s elementary school: “Dear Families, We wanted to inform you that we had an unusually high number of students across all grades suffering from symptoms of a stomach bug.”

One day before my 37th birthday, I had a parent-teacher conference in that building of horrors.

You know where this is going: I spent my birthday eve in the local E.R., getting fluids and the anti-nausea medication Zofran pumped into my veins. “You need to break the barf cycle,” the attending doctor said.

The ailment sweeping my kid’s school and my intestines was norovirus, a highly contagious stomach bug that causes nausea, vomiting and diarrhea. There are multiple strains of norovirus, so you can catch it more than once in a season — and it’s basically hanging around all winter, from November to April.

Norovirus can live on surfaces for days and, per the Centers for Disease Control and Prevention, people infected with norovirus shed billions of virus particles for two weeks or more; just a few particles can make other people sick. That’s why norovirus outbreaks have caused an elementary school in Seattle and 40 schools in Colorado to close briefly in recent weeks — officials wanted to stop the spread, and keeping sick kids away from each other and the building can help.