Many years ago, (more than 20) my friends and I, while playing our weekly game of Risk started talking about if we were terrorists, how would we maximize damage to our intended targets. This was before food trucks became all the rage.
One of my friends suggested that posioning the water for dirty water hot dogs would be the way to go. Most carts are run by Arabs, and thousands of people eat at them every day. If you had a biological agent, think of all the people getting on Mass transit on a Friday afternoon.
On the other hand, someone suggested dropping a bio agent in a Gaza open air market the afternoon of their sabbath. Then when the ensuing panic hits Gaza, Israel prevents anyone from entering the country until the problem is resolved.
We figured if we could think of this, others would also. Never ate a dirty water dog in NYC after that.
Never ate hotdogs from vendors in the city either.