However, there is no agreed cut-off after which COVID-19 can be excluded as a likely cause and sadly, some people die from their infection many weeks later.
Fodd bynnag, nid oes yna gyfnod amser penodol ar gyfer pryd y gellir diystyru COVID-19 fel achos tebygol ac, yn anffodus, mae rhai pobl yn marw o'u haint wythnosau lawer yn ddiweddarach.