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Box 6: Climate and cholera

The bacterial species responsible for cholera proliferate in warm waters. Copepods, tiny zooplankton that feed on algae, can serve as reservoirs for Vibrio cholerae and other enteric pathogens. In Bangladesh, cholera follows seasonal warming of sea surface temperature that can increase plankton blooms. El Niño and La Nina events seem to intensify the pattern of cholera incidence - cholera increases after warm events and decreases after cold events (Rodo and others 2002, Kovats and others 2003).

Emissions of carbon dioxide, methane, and other greenhouse gases from land use change and industrial activities are contributing to climate change, and thus may be indirectly involved in emerging and re-emerging infectious diseases (IPCC 2000).

Changes in climate inevitably lead to changes in habitat and a resultant change in the location of vectors (Kovats and others 2003). While the net effect globally remains uncertain and somewhat controversial (Reiter 2001, Hay and others 2002, Confalonieri 2003), local changes in the risk of vector borne infectious disease are virtually certain (Patz 2002). Certain microbial organisms, such as Neisseria meningitidis, a common cause of meningitis, can be borne many miles on the wind in dusty conditions following exacerbated droughts in the Sahel (Cunin and others 2003). Cholera outbreaks are also influence by climate events such as El Niño (Box 6).

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