of the 20,490 positive cases that were eligible for follow-up, 18,393 (89.8%) were reached and asked to provide details of their recent contacts
o blith y 20,490 o achosion positif a oedd yn gymwys i'w holrhain, cyrhaeddwyd 18,393 (89.8%) a gofyn iddynt ddarparu manylion y bobl y maent wedi dod i gysylltiad â nhw yn ddiweddar