I went on a school trip once, and it involved a several hour bus ride out to a processing plant and we were staying in a college type place which had a canteen, so everyone in the morning while having breakfast then had to make themselves sandwiches for lunch from a buffet type setup.
The most popular choice of sandwich was chicken, I on the other hand, having an incling that the bus doesn't have a fridge AND it was January in Central Queensland (40 degrees), chose Salami instead figuring cured meat would be pretty safe.
Luckily it payed off, the sandwiches we all made went into a Styrofoam box into the luggage area under the bus...
Everyone who had chicken got food poisoning.