What does they have watered the street mean? in figurative language

people are gonna need the passage.

martians or other types of aliens represent a unique fear as opposed to zombies. vampires and other types of monsters.   in most sci-fi stories, aliens come from other worlds and have different or more advanced technology.   abductions and experimentation on human bodies that involve these technologies, or the use of these technologies against human beings and the use of unknown "powers", are a type of fear that's different from that of other types of monsters.  

the red coloration of the lungs looks alarming and adds to the overall message that the flu is threatening apex