The Santa Barbara County Public Health Department announced the fourth case Monday. All four people became infected last month and one of the patients had to have both feet amputated, the Associated Press reported.
The first two confirmed cases of meningococcal disease involved male students, the first of whom fell ill Nov. 11. The fourth case also expanded the group of people potentially exposed from 300 to 500, health officials said.
The university previously announced it was bolstering its cleaning procedures in residence halls, the recreation center and sports facilities.
Meningococcal disease is bacterial and causes bloodstream infections and meningitis. College students, especially those living in residence halls, are prone to contracting the disease because of their close proximity to each other.
The disease causes high fever, severe headaches, rash and increased sensitivity to light, according to health officials.
To avoid getting the illness, health officials advise such precautions as washing hands frequently, not sharing utensils or water bottles, staying home when sick, keeping away from others who are ill, and covering one's mouth when sneezing and coughing.
Smokers are at increased risk of meningococcal infection, officials said.