It might spread outside the city limits to my neighborhood. Tactical neutron weapons could do the job nicely.
Either that or she puts a bag over his head when they have sex.
Diseases and plagues don't respect city limits any more than thugs respect "Gun Free Zone" signs or concealed carry compliance documents.
Examples: standing water pooled in tires on top of open ships taking tires to the US carried mosquitoes bred, hatched and spread Asian viruses several times.
When cargo doors opened on airport arrival of planes from Asia the trapped bugs and especially mosquitoes came out of the back and hid in the tall weeds of airport perimeters and spread virus to US. Detroit Metro story.