There's a moderately alarmist article here about the shipping of pathogens:
Every day, deadly germs are shipped across the country and around the globe, right alongside the books, gourmet foods and birthday presents sent through FedEx Corp. and similar couriers.I have to say, I don't see a lot of reason to be paranoid about legitimate labs shipping pathogens via legitimate couriers; IATA and FedEx overpack regulations for infectious substances and diagnostic specimens are very strict, and the packaging can withstand just about any accident it's likely to have. I'm far more concerned about mishandling or malice at the receiving end. In most cases, the labs themselves are far more dangerous than transportation, both in terms of accidentally infecting people (as thus), and providing pathogens to people who shouldn't have them (as thus).
Often their journeys can be circuitous, too.
Follow, for instance, a single vial of the potentially deadly flu virus causing a world health scare because it was included in test kits sent to more than 4,000 laboratories. It was grown in a Virginia lab, spent time in a Cincinnati freezer and passed through a small medical company on the Mexican border before it finally arrived at a Milwaukee lab.