Effects of Large-Scale Oceanic Phenomena on Non-Cholera Vibriosis Incidence in the United States: Implications for Climate Change

Abstract

PurposeEpidemics of diarrhea caused by toxigenic strains of Vibrio cholerae are of global public health concern, but non-cholera Vibrio (NCV) species are also important causes of disease. These pathogens are thermophilic, and climate change could increase the risk of NCV infection. The El Nino Southern Oscillation (ENSO) is a "natural experiment" that may presage ocean warming effects on disease incidence. MethodWe obtained vibriosis case counts in the United States by digitizing annual reports from the U.S. Cholera and Other Vibrio Illness Surveillance system. Trends and environmental impacts (of ENSO and the North Atlantic Oscillation) were evaluated using negative binomial and distributed nonlinear lag models. Associations between latitude and changing risk were evaluated with meta-regression. ResultsTrend models demonstrated significant seasonality (P < 0.001) and a 7% annual increase in disease risk from 1999 to 2014 (annual IRR 1.071, 95% CI 1.061-1.081). Distributed lag models demonstrated increased vibriosis risk following ENSO conditions over the subsequent 12 months (integrated RR 1.940, 95% CI 1.298-2.901). The rate of change in vibriosis risk increased with state latitude (RR per 10{degrees} increase 1.066, 95% CI 1.027-1.107). ConclusionVibriosis risk in the United States appears to be impacted by irregular large-scale ocean warming and exhibits a north-south gradient in rate of change as would be expected if changing disease incidence is attributable to ocean warming. Vulnerable populations, which include high-income countries with well-developed public health systems, may experience increased risk of this disease as a result of climate change.