[@QT]
The infection spreads mostly through the water. 

The infected want the non infected to help them. Their hostility could cause scratches and other open sources. the spores are only released after the infected has died. Rain could contain small amounts of these spores as well. 

Though the mouth is left untouched this is for keeping the host alive, rather than biting.

More information will be scattered about the city( When I do ever find a map) at certain undisclosed points. Your characters would know little to nothing about the infection. Other than it spreads through water.