Actually that's pretty cool - that's what plagues are supposed to do.

Btw, it's not that odd to see Syrakousai wracked with plagues every now and then - it is a very large city after all, and RTW actually does work a bit according to Malthus' positive checks.

Also Eburonum etc. are part of the Amber route and thus are part of the "disaster hit zone" for plagues in descr_disasters.txt. (As is the case with all settlements on the Persian Royal Road or Silk Route.)