translation.da: Med skiftende intervaller, sædvanligvis nogle få tiår, dukker et nyt influenzavirus op, som er ukendt for alle eller næsten alle mennesker, og det betyder, at mennesker kan have ringe immunitet, undtagen ældre mennesker, som kan have mødt det samme virus.
translation.en: At irregular intervals, usually of a few decades, a new influenza virus emerges which is novel to all or most people which means that there can be little specific immunity among humans except for older people who may have met unless they met the same virus.