translation.en: Due to a series of factors, a very low proportion of carriers (less than 1%) will eventually become ill. This most frequently occurs in young children, but a second disease peak is observed among adolescents and young adults.
translation.is: Af ýmsum ástæðum verður mjög lágt hlutfall smitbera (minna en 1%) að lokum veikt. Það gerist oftast hjá ungum börnum, en annar toppur á sér stað meðal unglinga og ungs fólks.