The bacteria that causes Legionnaires' disease were found in the hot-water systems of buildings at West Chester University last week, causing hot water to be shut off to nine buildings over the weekend until the systems were sanitized.
It was the second time this summer that the bacteria have been found on the campus.
On Monday - the first day of classes - the remediation company hired to handle the problem reported that the systems had been successfully sanitized, a university spokeswoman said.
She added that the university plans to set up a protocol with the remediation company in case the bacteria return.
Marisa Brown, 20, said she got a health alert from the university but initially thought the message was referring to the bacteria found in July. Then her mother called her. Then her best friend called.
"She said, 'My mom is freaking out.' And I said, 'So is mine,' " said Brown, who sat in a lounge area Monday morning in Main Hall, one of the affected buildings.
"It is kind of scary," she said.
The school said there was no cause for concern over the new bacteria, which were discovered during voluntary testing the university ordered after the July scare.
That month, an employee contracted Legionnaires' disease, a severe form of pneumonia.
The school tested the cooling towers on campus and found the bacteria in eight buildings. They were treated last month.
The university then decided to test other systems on campus.
"We thought, 'If it could be in the cooling towers, what about the hot-water systems?' " said Loretta MacAlpine, a university spokeswoman.
The test results came back late Thursday. This time, the bacteria were found only in classroom and administrative buildings. Residence halls were not affected and did not have their hot water shut off.
Students, faculty, and staff were notified Friday, MacAlpine said. Over the weekend, the hot water in the affected buildings was turned off, and the systems were treated to kill the bacteria, the university said.
Legionnaires' disease is contracted by inhaling the bacteria through water droplets. It is not contagious.
Experts said the presence of the bacteria, which are commonly found in water, did not necessarily mean the employee had contracted the disease at the university.
The disease is not spread through drinking water. Though some students, including Brown, said they planned not to drink the campus water, MacAlpine said it posed no threat.
She said that the university was working to keep students and parents informed and that she had been fielding calls from concerned parents.
Some students on campus Monday said they were not worried. But there had been some chatter about the bacteria at freshman orientation Saturday.
Alyson Layser, a freshman, said she was among those not worried. She is commuting to campus from Collegeville, "so I'm not going to be here all the time."
On Monday afternoon, she sat outside Green Library, where cooling towers tested positive for the bacteria in July. She has a class in at least one of the newly sanitized buildings.
The school and the Chester County Health Department said there was no need to halt university activities. "Safe hot water" is now running in all campus buildings, MacAlpine said.
"There's really no immediate cause for concern," she said.
There have been no cases of the disease on campus aside from the employee in July.
The bacteria were detected in Anderson Hall, Main Hall, Merion Hall, Messikomer Hall, Peoples Building, Ruby Jones Hall, Schmucker Science Center South, Speakman Building, and 13/15 University Ave., the university said.