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Occurrence and growth of Vibrio cholerae, the causative agent of cholera, is linked to modalities of elevated temperatures and heavy precipitation. Previous studies have employed temperature- and s...

The ability to predict an occurrence of cholera, a water-related disease, offers a significant public health advantage. Satellite based estimates of chlorophyll, a surrogate for plankton abundance, have been linked to cholera incidence. However, cholera bacteria can survive under a variety of coastal ecological conditions, thus constraining the predictive ability of the chlorophyll, since it provides only an estimate of greenness of seawater. Here, a new remote sensing based index is proposed: Satellite Water Marker (SWM), which estimates condition of coastal water, based on observed variability in the difference between blue (412 nm) and green (555 nm) wavelengths that can be related to seasonal cholera incidence. The index is bounded between physically separable wavelengths for relatively clear (blue) and turbid (green) water. Using SWM, prediction of cholera with reasonable accuracy, with at least two month in advance, can potentially be achieved in the endemic coastal regions.

Few regions in the world are nearing a large-scale water crisis as rapidly as South Asia, especially the basins in the Eastern Himalayas. Despite being known to be a water-rich part of the world, lack of integrated planning, and unfavourable natural and political settings have pushed this populous region towards basin-wide water scarcity, flood hazards, water quality and ecosystem degradation, and public health problems. Rapid growth of population and an unforgiving future climate complicate the situation and put millions more at risk. Meanwhile, the riparian nations continue unilateral efforts to develop their water resources without addressing the ecological integrity of the complex transboundary river system. This article provides an overview of the asymmetry in hydroclimatic conditions and unhelpful political realities that have pushed the region towards a looming large-scale water conflict.

Vibrio cholerae is an estuarine bacterium associated with a single peak of cholera (March-May) in coastal villages of Bangladesh.For anunknownreason, however, cholera occurs in a unique dual peak (March-May and September-November) pattern in the city of Dhakathat is bordered by a heavily polluted freshwater river system and flood embankment. In August 2007, extreme flooding was accompanied by an unusually severe diarrhea outbreak in Dhaka that resulted in a record high illness. This study was aimed to understand the unusual outbreak and if it was related to the circulation of a new V. cholerae clone. Nineteen V. cholerae isolated during the peak of the 2007 outbreak were subjected to extensive phenotypic and molecular analyses, including multilocus genetic screening by polymerase chain reaction (PCR), sequence-typing of the ctxB gene, and pulsed-field gel electrophoresis (PFGE). Factors associated with the unusual incidence of cholera were determined and analysis of the disease severity was done. Overall, microbiological and molecular data confirmed that the hypervirulent V. cholerae was O1 biotype El Tor (ET) that possessed cholera toxin (CT) of the classical biotype. The PFGE ( Not I) and dendrogram clustering confirmed that the strains were clonal and related to the pre-2007 variant ET from Dhaka and Matlab and resembled one of two distinct clones of the variant ETconfirmed to be present in the estuarine ecosystem of Bangladesh. Results of the analyses of both diarrheal case data for three consecutive years (2006-2008) and regional hydroclimatology over three decades (1980-2009) clearly indicate that the pattern of cholera occurring in Dhaka, and not seen at other endemic sites, was associated with flood waters transmitting the infectious clone circulating via the fecal-oral route during and between the dual seasonal cholera peaks in Dhaka. Circular river systems and flood embankment likely facilitate transmission of infectious V. cholerae throughout the year that leads to both sudden and off-season outbreaks in the densely populated urban ecosystem of Dhaka. Clonal recycling of hybrid ElTor with increasing virulence in a changing climate and in a region with a growing urban population represents a serious public health concern for Bangladesh. Keywords: Cholera; Vibrio cholerae; dual peak; flood; off-season; fecal-oral; clonal transmission (Published: 8 August 2011) Citation: Infection Ecology and Epidemiology 2011, 1 : 7273 - DOI: 10.3402/iee.v1i0.7273