For cases in halls of residence, students may have been contacted by text or by their university to advise them to isolate and not by the local contact tracing team.
Ar gyfer achosion mewn neuaddau preswyl, mae'n bosibl derbyniwyd myfyrwyr tecst neu gysylltiad gan eu prifysgol i'w chynghori i ynysu, ac nid gan y tîm olrhain cysylltiadau lleol.