Wiktionary
spill over
vb. 1 To enter into another zone by way of accident or overcrowding; to overflow. 2 (context intransitive English) Of an infectious disease, to spread from one species of animal to another and particularly to humans.
WordNet
spill over
v. overflow with a certain feeling; "The children bubbled over with joy"; "My boss was bubbling over with anger" [syn: bubble over, overflow]
be disgorged; "The crowds spilled out into the streets" [syn: spill out, pour out]