GOV.WALES uses cookies which are essential for the site to work. Non-essential cookies are also used to tailor and improve services. By continuing to use this site, you agree to our use of cookies.
You are here:
Noun, Masculine, Singular
achosion gwreiddiol
Yr achos cyntaf o glefyd mewn poblogaeth benodol, nid o reidrwydd yr achos cyntaf a ddogfennir gan yr awdurdodau.
Cymharer ag 'index case' / 'achos cyfeirio'.