It is spread by coughs and splutters, not by clothing or bedding. At any one time, up to one in six of us carry it in our nasal passages without any particular symptoms. There are many different sorts of meningococcus called groups. These are based on differences in the outer coating. Once you have carried any of the meningococci, you develop protective antibodies to ALL of the groups.
Most adults have protective antibodies.
Certainly being a university student is not the only factor. Dr Keith Neal of Nottingham University surveyed 75 universities over three years. He thought that living in halls of residence as opposed to home could be a cause. On top of this, we had the Measles Rubella Campaign in 1994 when about seven million five to sixteen year olds were vaccinated - some for the second and third time against measles. These are the people who are going through university now.