Global spread of microorganisms by ships

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Ballast water discharged from vessels harbours a cocktail of potential pathogens.


Commercial ships have spread many species around the world1,2,3, but little is known of the extent and potential significance of ship-mediated transfer of microorganisms3,4. Here we show that the global movement of ballast water by ships creates a long-distance dispersal mechanism for human pathogens and may be important in the worldwide distribution of microorganisms, as well as for the epidemiology of waterborne diseases affecting plants and animals.

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Figure 1: Chesapeake Bay, on the US East Coast, receives some ten billion litres of foreign ballast water each year.


Figure 2: Prevalence and concentration of Vibrio cholerae serotype O1 and O139 in ships' ballast water.


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Correspondence to Gregory M. Ruiz.

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