Ocean warming has continued unabated, owing to climate change. (1) Water has a much larger capacity to absorb heat than the atmosphere; thus, the heat content of the oceans has increased disproportionally. In fact, >90% of accumulated heat from global climate change is absorbed by the oceans, masking and slowing land surface warming. (1) The ocean warming process has accelerated over recent years and resulted in a range expansion of tropical marine species to higher latitudes and altered marine ecosystems. (1) Vibrio pathogens are part of these marine ecosystems, and their spread is being accompanied by human exposure and related illnesses and mortality, as well as their associated costs. (2)
Vibrio species are physically attached to tiny planktonic crustaceans known as copepods, which serve as the host organism in this commensal relationship. (3) These bacteria can cause large-scale cholera epidemics or sporadic infections, mainly as a result of consumption of uncooked seafood or exposure to recreational seawater. Twelve Vibrio species are associated with infections in humans. These include V. cholerae (serogroups O1 and O139), the causative agent of cholera epidemics. Another three species-V. parahaemolyticus, V. alginolyticus, and V. vulnificus--can cause sporadic but potentially severe gastrointestinal illnesses and wound infections, which can advance to outcomes such as necrotizing fasciitis, amputation, septicemia, and death. (4) The disease burden from these noncholera Vibrio infections is not extensive, but the incidence is increasing. (4)
Vibrio bacteria thrive in warm, brackish water and have expanded their habitat owing to the warming of the oceans. (5-7) In the summer of 2004, an outbreak occurred in Alaska as a result of the consumption of raw oysters contaminated with V. parahaemolyticus, >1,000 km north of any previously recorded infection with this pathogen. (8) Similarly, V. parahaemolyticus has appeared in northern Spain, (9,10) where ocean warming has also contributed to the spread of pathogenic Vibrio bacteria. (11) There has been a documented cross-oceanic migration and northbound expansion of plankton in response to the warming of oceans, (12) and it is possible that Vibrio species are hitchhiking along with their hosts. (13)
A new study by Sheahan et al. (14) in this issue of Environmental Health Perspectives examines the influence of climate change on vibriosis in the United States and projects future health and economic impacts. The authors took advantage of an invaluable resource that is available only in the United States. The Centers for Disease Control and Prevention (CDC) started collecting Vibrio cholera case data in 1997 and expanded their national surveillance efforts to all vibriosis cases in 2007. (15) In contrast, there is no continent-wide surveillance data available for other Vibrio pathogens in Europe. For example, Vibrio cholera of serogroups O1 or O139 is a reportable disease in the European Union, but other Vibrio species are not. (16) The authors analyzed the CDC's rich Cholera and Other Vibrio Illness Surveillance (COVIS) database to address the study objectives. Although there are limitations to COVIS, such as underreporting and potential exposure misclassification, it is nevertheless unique and the largest...