Multiply the given value by four.
a quadruple room is room occupied by four people may have two beds or more...or a room with four single beds.
quadruple means anything that has 4 of something in it. quad=4
Mulitply your area by four
1x US-pig 1x Asian pig 1x Bird 1x Human = 4 viruses recombined = 4 sources = Quadruple source combinated to obtain 1 virus.
A horse is a quadraped quadra means four ped means foot a horse has four feet. quadruple means four times.