Climate change and water borne diseases, particularly cholera

1. Climate change and water borne diseases, particularly cholera G. Balakrish Nair, PhD FNA, FNASc, FTWAS, FAAM Director National Institute of Cholera and Enteric Diseases (Indian Council of Medical Research) Kolkata, India

3. This value is about the same as the global number of deaths from smoking, double the global number of deaths from HIV/AIDS, and 25 times the global number of death from warRudan et al., 2007. Lancet Infect. Dis. 2007; 7: 56-61

4. Five examples of climate and diarrhoea Pacific islands El Nino and diarrhea Diarrheal epidemics in Bangladesh Environmental signatures associated with cholera epidemics in Kolkata, India New variants of cholera in India

5. Annual average temperature and average reporting rates for DD, Pacific Islands (1986-1994)Singh et al, 2001s We carried out two related studies to explore the potential relationship between climate variability and the incidence of diarrhea in the Pacific Islands. In the first study we examined the average annual rates of diarrhea in adults as well as temperature and water availability from 1986 to 1994 for 18 Pacific island countries. There was a positive association between annual average temperature and the rate of diarrhea reports and a negative association between water availability and diarrhoea rates. In the second study, we examined diarrhea notifications in Fiji in relation to estimates of temperature and rainfall. There were positive associations between diarrhea reports and temperature and between diarrhea reports and extremes of rainfall.We carried out two related studies to explore the potential relationship between climate variability and the incidence of diarrhea in the Pacific Islands. In the first study we examined the average annual rates of diarrhea in adults as well as temperature and water availability from 1986 to 1994 for 18 Pacific island countries. There was a positive association between annual average temperature and the rate of diarrhea reports and a negative association between water availability and diarrhoea rates. In the second study, we examined diarrhea notifications in Fiji in relation to estimates of temperature and rainfall. There were positive associations between diarrhea reports and temperature and between diarrhea reports and extremes of rainfall.

6. Annual potential water availability and average reporting rates for DD, Pacific Islands (1986-1994)Singh et al., 2001

7. El Nino and diarrheal disease(potential effects of climate variation) El Nino linked with cholera and other diseases Marked increase in number of cases of diarrhea and dehydration in Lima, Peru during an El Nino event A two-fold increase in hospital admissions due to diarrhea during the winter of 1997-98 Drought in Fiji was associated with an increase in reported cases of infantile diarrhoea A two fold increase in hospital admissions was evident during th ewinter of 1997-1998, suggesting that El Nino has an effect on hospital admission for diarrhea which was far greater than that explained by seasonal temperature changes.A two fold increase in hospital admissions was evident during th ewinter of 1997-1998, suggesting that El Nino has an effect on hospital admission for diarrhea which was far greater than that explained by seasonal temperature changes.

8. Demographic, microbiologic and clinical data from patients presenting during 1988, 1998 and 2004 flood-associated diarrheal epidemics at a Diarrhoea treatment hospital in Dhaka were examined. Compared with non-flood periods, individuals presenting during flood associated epidemics were older, more severely dehydrated and of lower socioeconomic status. During flood associated epidemics, Vibrio cholerae was the most commonly identified cause of diarrhoea, and the only diarrhoeal pathogen whose incidence proportionally increased in each epidemic compared with seasonally matched periods. Rotavirus was the second most frequently identified flood-associated pathogen, although the proportion of cases cause by rotavirus infection decreased druing floods compared with matched periods. Other causes of diarrhoea did not proportionally change.Demographic, microbiologic and clinical data from patients presenting during 1988, 1998 and 2004 flood-associated diarrheal epidemics at a Diarrhoea treatment hospital in Dhaka were examined. Compared with non-flood periods, individuals presenting during flood associated epidemics were older, more severely dehydrated and of lower socioeconomic status. During flood associated epidemics, Vibrio cholerae was the most commonly identified cause of diarrhoea, and the only diarrhoeal pathogen whose incidence proportionally increased in each epidemic compared with seasonally matched periods. Rotavirus was the second most frequently identified flood-associated pathogen, although the proportion of cases cause by rotavirus infection decreased druing floods compared with matched periods. Other causes of diarrhoea did not proportionally change.

9. Cholera, caused by Vibrio cholerae, lends itself to the study of the role of climate in infectious disease This disease has a historical context linking it to specific seasons and biogeographical zones. Cholera and V. cholerae offer an excellent example of the effect of climate and weather on infectious diseases and pathogens. The model for environmental cholera transmission as proposed by Colwell and Huq suggest a hierarchy to interpret the significance of climate and the environment in cholera and V. cholerae dynamics. Among physical factors, temperature perhaps has the most direct and significant effect on the ecology of most bacteria. It is not any different for V. cholerae because warmer temperatures in combination with elevated pH and plankton blooms can influence its attachment, growth, and multiplication in the aquatic environment, particularly in association with copepods.Cholera, caused by Vibrio cholerae, lends itself to the study of the role of climate in infectious disease This disease has a historical context linking it to specific seasons and biogeographical zones. Cholera and V. cholerae offer an excellent example of the effect of climate and weather on infectious diseases and pathogens. The model for environmental cholera transmission as proposed by Colwell and Huq suggest a hierarchy to interpret the significance of climate and the environment in cholera and V. cholerae dynamics. Among physical factors, temperature perhaps has the most direct and significant effect on the ecology of most bacteria. It is not any different for V. cholerae because warmer temperatures in combination with elevated pH and plankton blooms can influence its attachment, growth, and multiplication in the aquatic environment, particularly in association with copepods.

11. Location and methods for estimation of parameters Satellite sensors used to measure CHLa conc and SST; rainfall was also measured by SS and by in situ gauge Monthly number for culture confirmed cholera cases at the ID Hospital Kolkata, and ICDDR,B hospital, Matlab

12. A statistically significant relationship was observed between the nine-year cholera cases time series and both chlorophyll a concentration and rainfall anomalies. The interannual variability of cholera and occurrence of a strong El Nino in 1998, associated with the larges number of cholera cases for both Kolkata and Matalab in that year offers challenging examples of cholera and climate interaction A statistically significant relationship was observed between the nine-year cholera cases time series and both chlorophyll a concentration and rainfall anomalies. The interannual variability of cholera and occurrence of a strong El Nino in 1998, associated with the larges number of cholera cases for both Kolkata and Matalab in that year offers challenging examples of cholera and climate interaction

14. Comparative study of the dynamics of cholera in India 1999 to 2007 The figure show, by month, the number of cholera cases, confirmed by culture, at the two locations and the seasonal patterns computed for the 8 year time period. The seasonal pattern of cholera in Kolkata begins in April, with the largest number of cases appearing between August and October. The seasonal pattern in Delhi is more pronounced and the largest number of cholera cases occur between May and August, progressively decreasing thereafter.The figure show, by month, the number of cholera cases, confirmed by culture, at the two locations and the seasonal patterns computed for the 8 year time period. The seasonal pattern of cholera in Kolkata begins in April, with the largest number of cases appearing between August and October. The seasonal pattern in Delhi is more pronounced and the largest number of cholera cases occur between May and August, progressively decreasing thereafter.

16. Literature Search PubMed �India� and �cholera� 1134 identified/500 were included �Acute watery diarrhoea/diarrhea� �India� Additional Search Freemedical journals Medexplorer Medscape Medhunt

21. Cholera and Climate Change Cholera epidemics are influenced significantly by climate and several environmental drivers have been proposed to explain the seasonal cycle of cholera Copepods serve as hosts of Vibrio cholerae (carapace and gut, 103-105) and thereby serving as vectors of this pathogen Vibrio cholerae, cannot be sensed directly but its presence can be inferred using remote sensing data Discovered that sea surface temperature shows an annual cycle similar to cholera case data Additionally sea surface height correlated with cholera outbreaks Provided strong evidence that cholera epidemics are climate-linked Although the bacterium, V. cholerae, cannot be sensed directly, remotely sensed data can be used to infer its presence. Satellite data has been used to monitor the timing and spread of cholera. Public domain remote sensing data for the Bay of Bengal were compared directly with cholera case data collected in Bangladesh from 1992�1995. The remote sensing data included sea surface temperature and sea surface height. It was discovered that sea surface temperature shows an annual cycle similar to the cholera case data. Sea surface height may be an indicator of incursion of plankton laden water inland, e.g., tidal rivers, because it was also found to be correlated with cholera outbreaks. The extensive studies accomplished during the past 25 years, confirming the hypothesis that V. cholerae is autochthonous to the aquatic environment and is a commensal of zooplankton, i.e., copepods, when combined with the findings of the satellite data analyses, provide strong evidence that cholera epidemics are climate-linked. Although the bacterium, V. cholerae, cannot be sensed directly, remotely sensed data can be used to infer its presence. Satellite data has been used to monitor the timing and spread of cholera. Public domain remote sensing data for the Bay of Bengal were compared directly with cholera case data collected in Bangladesh from 1992�1995. The remote sensing data included sea surface temperature and sea surface height. It was discovered that sea surface temperature shows an annual cycle similar to the cholera case data. Sea surface height may be an indicator of incursion of plankton laden water inland, e.g., tidal rivers, because it was also found to be correlated with cholera outbreaks. The extensive studies accomplished during the past 25 years, confirming the hypothesis that V. cholerae is autochthonous to the aquatic environment and is a commensal of zooplankton, i.e., copepods, when combined with the findings of the satellite data analyses, provide strong evidence that cholera epidemics are climate-linked.

22. Spread of V. cholerae O139 Bengal in India during 1992-93

28. Outbreak of Cholera-like Diarhoea in Orissa, India

30. Global surface temperature, based on surface air temperature measurements at meteorological stations and on sea surface temperature measurements from ships and satellites, shows a temperature increase of 1.4�F (0.78�C) since the beginning of the 20th century, with about 1.1�F (0.61�C) of the increase occurring in the past 30 years.Global surface temperature, based on surface air temperature measurements at meteorological stations and on sea surface temperature measurements from ships and satellites, shows a temperature increase of 1.4�F (0.78�C) since the beginning of the 20th century, with about 1.1�F (0.61�C) of the increase occurring in the past 30 years.

32. Strategies to mitigate the effect of climate change Current strategies for controlling infectious disease epidemics rely primarily on surveillance and response The recommendation now is a shift towards prediction and prevention, such as developing early warning systems Overall vulnerability to infectious disease could be reduced through water treatment systems, vaccination programs and enhanced efforts to control disease carriers.

33. Future plan of actions Carry on the work on impact assessment through prospective surveillance Developing a robust disease surveillance system Develop an appropriate predictive model for an EWS for diarrhoeal outbreaks