A Georgetown spokeswoman, Meghan Dubyak, pointed out that last year was Washington’s wettest on record, and that the university had “initiated proactive steps to prevent mold and promptly respond to all reported cases within two business days.” She added that the Georgetown board of directors had recently allocated $75 million to improve campus infrastructure, with a focus on student residences.

Facilities workers at several universities acknowledged that there were dismal conditions in some buildings on their campuses, and pointed to aging infrastructure, shortages of funds and a lack of political will to make upkeep a priority. They said they were forced to focus on reactive maintenance, fixing problems as they came up, rather than creating and following a comprehensive maintenance plan.

“It’s all gotten so bad for many, many years that now it’s reaching the breaking point,” Mr. Lyons said. “Frankly, some of these conditions are disgusting.”

Sometimes the effects on students can be long-lasting.

Not long after Sarah Melton moved into her University of Oklahoma dormitory last fall, she came down with a rash, headaches and cold symptoms. Soon she was having mood swings.

By November, she had withdrawn from the university and tested positive for mold poisoning. She has since transferred to a school in Texas, her home state, and said she was optimistic about the future. But she remains worried about any lasting effects of the problems she had while at Oklahoma.

Kesha Keith, a spokeswoman for the university, said she could not comment on individual cases. She said the school had taken many steps to keep residence halls clean, including hiring a contractor to treat air units and bathroom vents in every residence-hall room.

“This unfortunately has become more of a lifelong issue,” said Ms. Melton, 19, who has been encouraging other college students to look for signs of mold when they move into their dorms. “I wish I would’ve just walked into the bathroom and looked up. We never thought to do that.”