(...) From air monitoring stations set up in the Virgin Islands, and from samples taken in Africa, Kellogg found that not only were microbes able to travel the thousands of miles from Africa, but that nearly a third of those that survived were known pathogens. In the right circumstances, they could cause disease in plants, livestock or humans, although only humans with a poorly developed or suppressed immune systems were likely to contract infections.  Read the entire GuardianUnlimited article...

At a NASA website you'll find a lot more about the shifting dust and soil across our earth. For example:

(...) This constant reshuffling of the world's sand and dust ties the continents together and serves as a reminder that, in the natural world, there are no political boundaries. Airborne microbes and pollen in Florida or Brazil might have come from Africa. Mineral dust in the soils of India could have blown over from Iran.

(...) In fact, over vast stretches of geologic time, the action of wind thoroughly mixes and re-mixes the world's dust. So the soil in your own backyard might contain some grains of dust from places all over the globe!   

(...) While much of this reshuffling of earth can't be seen by satellites, dust often migrates in huge clouds that show up in satellite images.   

(...) For example, the Americas frequently inherit huge volumes of dust from Africa and Asia, while countries of the Far East like India and China get sprinkled with dust from the Middle East.

(...) African dust plumes begin their trans-Atlantic journey with storm activity in the Sahara Desert region. The dust, originating from fine particles in the arid topsoil, is transported into the atmosphere by winds and may be carried more than 10,000 feet high. Dust clouds cross the Atlantic Ocean and reach the Caribbean and the Americas in about 5 to 7 days.

(...) Our planet's atmosphere provides a transcontinental highway for dust that's been stirred up from dry soils by strong winds. Because dust particles are so small -- often less than 0.002 mm across -- they can remain aloft for days as they ride global rivers of air. Larger sand grains don't get airborne as often or for as long, but they can be pushed along the ground by the wind or washed away by water erosion. 

You can watch airborne dust migrate around the globe at the  aerosol homepage for NASA's Total Ozone Mapping Spectrometer ( "TOMS"). Although the primary function of TOMS is to monitor the ozone layer, it also measures aerosols -- that is, airborne dust, smoke, and other particulates. NASA scientists use these data to create daily maps and movies that they post online. Visit the NASA site, "All the world is a stage for dust."  If you get lost, the "Dust Movie" is Here...