Smallville Press Release!

Episode 9x03 "Rabid"

ZOD UNLEASHES A VIRUS INTO METROPOLIS

Zod (Callum Blue) and his soldiers release a virus into the air that turns humans into zombies. The only way to stop it is to make an antidote from the blood of another Kryptonian. After Lois (Erica Durance) is infected, Chloe (Allison Mack) pleads with Clark (Tom Welling) to donate his blood to stop the epidemic, even though it risks outing him to Zod. Michael Rohl directed the episode written by Jordan Hawley

Source: CW