Epidemiological Investigation of a Diarrhea Outbreak in the South Pacific Island Nation of Tuvalu during a Severe La Niña–Associated Drought Emergency in 2011

Abstract

Abstract. The association between heavy rainfall and an increased risk of diarrhea has been well established but less is known about the effect of drought on diarrhea transmission. In 2011, the Pacific island nation of Tuvalu experienced a concurrent severe La Niña-associated drought and large diarrhea outbreak. We conducted a field investigation in Tuvalu to identify factors that contributed to epidemic transmission in the context of a drought emergency. Peak case numbers coincided with the nadir of recorded monthly rainfall, the lowest recorded since 1930. Independent factors associated with increased risk of diarrhea were households with water tank levels below 20% (odds ratio [OR] = 2.31; 95% confidence interval = 1.16-4.60) and decreased handwashing frequency (OR = 3.00 [1. .08]). The resolution of the outbreak occurred after implementation of a hygiene promotion campaign, despite persistent drought and limited water access. These findings are potentially important given projections that future climate change will cause more frequent and severe droughts.

A global review of the microbiological quality and potential health risks associated with roof-harvested rainwater tanks

“…A case-control study was conducted in July 2014 in response to a large 2011 diarrheal outbreak (n = 244 cases) that occurred concurrently with a La Niña-associated drought emergency on the Pacific island nation of Tuvalu, to identify factors that contributed to epidemic transmission. 94 The population is highly dependent on RHRW for potable water as well as government or community tanks filled with water treated with reverse osmosis. Seventy-five randomized case subjects were selected for administering a household survey and enrolled.…”

“…The authors propose that the rainwater association could be due to drought conditions limiting the availability of (cleaner) rainwater, and that households may switch to untreated or less hygienic sources; low residual volume in RHRW tanks may concentrate pathogens or reduce the ability to dilute introduced pathogens, increasing the likelihood of consuming a greater dose; or increasing the contaminant load during prolonged dry spells in between first flushes. 94 The findings from epidemiological studies indicate that RHRW can provide a decreased risk of diarrheal illness compared to consuming alternative or unimproved water sources. However, when risks are evaluated for RHRW relevant to other sources (such as "improved" water sources), this comparison is contingent upon the quality and context of the alternative water source and does not provide information on absolute risk and its relationship to risk acceptability benchmarks.…”

El Niño Southern Oscillation (ENSO) and Health: An Overview for Climate and Health Researchers

“…In the Pacific Islands, where diarrhoea is the most significant water-borne disease and ENSO has marked impacts on climate, there is a paucity of evidence for explicit El Niño-diarrhoea associations, although this is implied in a number of studies [80][81][82]. For West Africa, de Magny et al [83] suggested associations of diarrhoea with El Niño where ENSO, via the so-called Indian Oscillation and associated variations in large scale rainfall and temperature fields, may well influence cholera dynamics and thus diarrhoea.…”

El Niño Southern Oscillation (ENSO) and Health: An Overview for Climate and Health Researchers

“…In the Pacific Islands, where diarrhoea is the most significant water-borne disease and ENSO has marked impacts on climate, there is a paucity of evidence for explicit El Niñodiarrhoea associations, although this is implied in a number of studies [81,82,83]. For West Africa, de Magny et al [84] suggested associations of diarrhoea with El Niño where ENSO, via the so-called Indian Oscillation and associated variations in large scale rainfall and temperature fields, may well influence cholera dynamics and thus diarrhoea.…”