Pot Spring Elementary School

Pot Spring Elementary is one of the most overcrowded schools in the central corridor. It has a state-rated capacity of 477 students, but opened the 2012-2013 school year with 657 students. BCPS projects that number to rise to 664 in 2013, 683 in 2015, and 696 in 2018. (Photo by Jon Meoli / May 9, 2013)

Norovirus was likely the culprit that sickened 200 students and nine staff members at Pot Spring Elementary in Timonium last week, Baltimore County health officials have found.

About a third of the school's students were absent May 17 because of gastrointestinal symptoms, prompting a health department investigation. Preliminary lab tests performed by the county health department showed that norovirus was probably behind the symptoms, according to a letter the school's principal sent to parents this week.

Norovirus is highly contagious and the most common cause of stomach illness in the United States, according to the U.S. Centers for Disease Control and Prevention.

"The good news is that we saw enrollment rebound this week and get back to normal levels," schools spokesman Charles Herndon said Friday. "It appears that it has run its course."