During the cold open, the soon-to-be victim surreptitiously reports a "ten-thirteen" upon spotting his suspect. 10-13 is the New York police code for requesting backup; Boston, where this episode is set, is more likely to use the APCO system, in which 10-13 is a request for advice on weather and road conditions. He more accurately should have called 10-33.
Just before the subway train arrives, the signal changes from Danger to Clear, but when Doggett sees the train, it's coming from the opposite direction.
Despite being a CDC Contaminant specialist, Dr. Hellura Lyle leaves exposed skin under her face mask at the neck area.