The Role of El Niño – Southern Oscillation in Shaping Cholera Disease Dynamics: The Case of Bangladesh
Cholera remains a major public health problem in many developing nations. Areas with large cholera epidemics include Bangladesh, India and countries in Africa and South Africa (Kovats et al., 2003). Figure 1 shows areas that reported cholera outbreaks in 2009-2010. Traditionally, cholera has been viewed as a fecal-oral infection (Constantin de Magny et al., 2008). Prior to the 1970s, cholera was argued to be transmitted through person-person con- tact, where epidemics started with contaminated water and food (Constantin de Magny et al., 2008). More recently, the environmental determinants of the disease have been recognized, since Vibrio cholerae, the bacteria causing Cholera, is found to inhabit coastal waters, estuaries, and rivers (Pascual et al. 2000) Outbreaks of cholera emerge when V. cholerae is present in food and drinking water, and thus, are more likely to occur in regions with limited or damaged infrastructure (Cash et al., 2005). A growing body of research has emerged concerning the correlation between cholera epidemics and climate variability associated with El Niño Southern Oscillation (ENSO) (WHO, 1999). Increased attention has been paid to ENSO and cholera since the re-emergence of cholera in 1991-1992 in Peru coincided with an El Nino event, which motivated the hypothesis that ENSO events may influence cholera dynamics (Pascual, 2008). In addition, several outbreaks in 1997 in East Africa occurred, following heavy rains attributable to ENSO and because of an observed relationship between sea surface temperatures (SSTs) and cholera cases in coastal areas, most notably in Bangladesh near the Bay of Bengal (WHO, 1999).