Sheldon called Leonard to tell him as he predicted, his fever had been tracking up exponentially since 2 A.M and he started producing sputum at alarming rate. And the most important reason why Sheldon called Leonard is he wanted Leonard to bring him soup. That was also why Leonard run away immediately from the apartment when he heard Sheldon shouted to say he is sick. Also, Leonard lied Sheldon he was in lab at work even though it was Sunday morning at 6.
Leonard phoned Howard to warn him it was code milky green to refer Sheldon's always overreacting on fever. Howard forgot the protocol and picked up the Sheldon's call, and he immediately realized he made a mistake picking it up, so he imitated his mother's voice to tell Sheldon he was sleeping and hang up the phone.
exponentially: change rapidly.
track: narrow path
shift: change slightly
fever: your temperature gets higher than normal usually because you get a cold, and your heart hurts
centrifuge: a machine that spins very quickly to separate the different things mixed together.
infection: a kind of disease
ungodly: morally bad or opposed to religion, you can also describe a time that is very early as ungodly, for example 4 A.M in the morning.
