Mae'r frech goch yn lledaenu'n hawdd iawn ymhlith y rhai sydd heb eu brechu, yn enwedig mewn meithrinfeydd ac ysgolion. Gall plant sy'n dal y clefyd fynd yn sâl iawn ac, mewn rhai achosion, gall y frech goch arwain at orfod mynd i'r ysbyty ac, yn anffodus, mewn achosion prin, gall arwain at farwolaeth.
Measles spreads very easily among those who are unvaccinated, especially in nurseries and schools. Children who contract the disease can become very unwell and, in some cases, measles can lead to hospitalisation and in rare cases, tragically death.