On-flyge

According to the Old English Dictionary:

es;

on-flyge

m. Infectious disease, disease which, as it were, flies at people:--Ðú miht wið áttre and wið onflyge, Lchdm. iii. 32, 2, 16, 30. preceding word and ongeflogen; and cf. Icel. á-flog, flying at a person, fighting. on-flyge