Kraal virus
From Tardis Wiki, the free Doctor Who reference
The Kraal Virus was a virus created the Kraal scientist Styggron, and designed to kill off the Human species in three weeks, and then disappear, allowing the Kraal to conquer the plane without opposition.
The virus could be transmitted by touch or by ingestion, but not by air, meaning that the Kraal had to rely on their androids to transport the virus. (DW: The Android Invasion)
