Automobiles, cargo ships, and airplanes are much more effective transport vectors than the slow-moving caravans and sailing ships of the past. For example, every day fresh fruits and vegetables cross international borders and quickly end up on kitchen countertops, in refrigerators, and eventually in the bodies of people living thousands of miles away from the fields and orchards where the food was gathered. Safeguards that prevent the transportation of microbes are difficult to develop and enforce because of the multitude of infectious agents that can hitch rides in unusual places. Transoceanic ships carry a surprising number of organisms in their ballast waters-367 different species of marine organisms were identified in the ballast water of ships traveling between Japan and Coos Bay, Oregon. This mosquito has now become established in Hawaii and at least 20 U.S. states.
Aircraft are also efficient vehicles for transporting microbes.
Mosquitoes and other arthropods, such as flies and beetles, can survive temperatures down to -420 C within the wheel bays of aircraft for six to nine hours. Thus, the airplane has opened an entirely new route for infectious agents to travel not only between countries, but across continents. Infectious microbes from anywhere in the world can now reach most U.S. cities within 48 hours via commercial airlines, faster than the incubation period for many diseases. The new reality is that even the most vigilant public health efforts cannot prevent the import of infectious microbes and the vectors that transmit them. Most population movement occurs more slowly, and over land.