Source Water, Environment, and Disease Risk in North American Cities

1. Drink it In Source Water, Environment, and Disease Risk in North American Cities Amy L. Greer1, Victoria Ng1, Alexander White1 & David N. Fisman1,2 email: amy.greer@sickkids.ca 1The Research Institute of the Hospital for Sick Children 2Ontario Public Health Laboratories Branch

2. My presentation today Human health and the environment Hypothesis and methodology Examples: Norovirus, Legionellosis, Campylobacter and Giardia Moving towards a more integrated point of view

3. Water & Human Health

4. The Canadian Context Outbreaks of waterborne diseases in Canada have shown: • how easily water can be contaminated • how damaging the consequences can be (Greer et al., 2008)

5. A Multi-Barrier Approach • Source water protection • Effective water treatment • Protection of the water distribution system • Adequate testing and training

6. What is Source Water? • Source water is untreated water from streams, lakes or underground aquifers that supplies private wells and public drinking water systems • surface water (74% of Canadians) • groundwater (26% Canadians)

7. Source Water Ecology • Freshwater ecosystems include the animal, plant and microbial communities in lakes, rivers and ponds • Microbes such as bacteria, bacteria-like organisms , viruses, protozoa, helminths, and protists are vital components of the aquatic ecosystem

8. Environmental Reservoirs • Movement and persistence of microbes in the absence of human hosts • Exposure to few propagules can cause human infection • Multi-barrier approach is good for some pathogens but not others Multi-barrier Approach

9. Question & Hypothesis What environmental factors are associated with an increased frequency of outbreaks? Hypothesis:Environmental factors that increase pathogen survival, persistence or proliferation in the source water environment will be related temporally and spatially to human outbreaks

10. Victoria Ng & David Fisman Weather, Water & giardia in Philadelphia, 1994-2007

11. Giardia lamblia • Most common protozoan agent of diarrheal illness in North America • Late summer/early fall seasonality • Zoonotic • Cysts measure 7 to 14 μm • Cysts are resistant to extreme environmental conditions • Chlorine typically does not destroy the cysts

12. Cases with a History of Water Exposure

13. Cases with a Known Onset & History of Water Exposure An increase in the risk of giardiasis is seen with decreasing river level in the Schuykill River at a 24 to 26 day lag prior to case occurrence

14. Amy Greer, Steven Drews & David Fisman (www.news.bbc.co.uk) Seasonal Drivers of Norovirus Outbreaks in the Greater Toronto Area, 2005 - 2008

15. Norovirus • Norovirus is the most common, non-bacterial cause of gastroenteritis • “wintertime vomiting disease” • Source water contaminated by infected sewage or wastewater • 27 to 38 nm • Chlorination and filtration are considered insufficient to remove

16. Lake Ontario temperature ≤ 4 degrees C

17. High flow in the Don River

19. Victoria Ng & David Fisman (www.news.bbc.co.uk) Epidemiologic Profile of Legionellosis in the GTA: 1978 to 2006

20. Legionella sp. • Transmission occurs when people breathe in a mist or vapour contaminated with the bacteria • Late summer to early autumn predominance • Bacteria occur in all aquatic environments with their primary hosts, free-living protozoa • Chlorination and flushing of pipes has limited effect

21. Case-Crossover Results • Risk of infection increased with low river and creek levels. Acute effects were seen 25 to 31 days prior to case occurrence (OR 3.55, 95% C.I 2.38-5.29) • Risk of infection increased with decreasing lake temperature (OR 1.33, 95% C.I 1.08-1.64) with 25 to 28 day lag • Risk of infection increased with increasing humidity with 30 to 34 day lag (OR 1.34, 95% C.I 1.14 to 1.57)

22. GTA, average river and lake levels: OR 3.55 [95% C.I, 2.38-5.29] with 25 to 31 day lag

23. Similar Results Found in Three Major Cities • GTA, average river and lake levels: OR 3.55 [95% C.I, 2.38-5.29] with 25 to 31 day lag • Philadelphia, Schuykill River level: OR 2.48 [95% C.I, 1.39-4.42] with 25 to 31 day lag • Hamilton, Stoney Creek level: OR 5.24 [95% C.I, 2.07-13.29] with 25 to 28 day lag (OR 2.80 with 25 to 31 day lag)

24. Philadelphia, PA SchuylkillRiver Delaware River Alexander White & David Fisman (www.news.bbc.co.uk) Water & Campylobacter in philadelphia, 1994 - 2007

25. Campylobacter sp. • Leading cause of acute bacterial gastroenteritis in both developed and developing countries • Summertime seasonality • Zoonotic • Increased humidity and low water temperature increase campylobacter colonization and survival rates • Multi-barrier approach typically sufficient

26. Table 1 Univariate analysis of environmental risk factors Table 2 Multivariable analysis of environmental risk factors

27. Disease Risk and Environment • Microbes are present in the aquatic ecosystem • Some of these are pathogenic to humans • Environmental conditions can have an indirect impact on disease occurrence in the community by influencing the presence, persistence and proliferation of pathogens in the aquatic ecosystem • A better understanding of the mechanisms involved will help us to better mitigate the risks

28. Moving Beyond the Disciplines • A fully dimensional understanding of infectious disease reaches across scales • Medicine and public health is enriched by insights from across science and engineering Colon et al. 2008

29. Seeking Out A New Paradigm • Many pathogens infect humans through a wide variety of ecological pathways • Pathogens have complex and somewhat mysterious relationships with the environment • Health issues now encompass an individual's complex relationship with the global environment • Patterns of disease expand across scales, and explanations must move beyond old paradigms to explore these relationships