"Two." Another finger. "It’s not a quick kill, which has all sorts of advantages from the terrorist’s point of view. First, there’s the hysteria. Panic, xenophobia, scapegoating of various groups—all the stuff you read about with every plague in history. You’ll probably end up with lots of casualties among people who weren’t even exposed to the bug or the spell, and much greater demands on a city’s or country’s infrastructure.