WEPA 2nd International Workshop

February 23, 2011
Tokyo, Japan

Risk of Infectious Diseases
during Flood and Drought
Toru Watanabe
Dept Food, Life & Environmental Sciences
Yamagata Univ, JapanSelf-introduction
Toru Watanabe
Ph.D. in Civil & Environ. Eng. (Tohoku Univ., Japan, 2006)2010 - present Associate Professor, Faculty of Agriculture,
Yamagata Univ., Japan
2009 - 2010
Project Assoc. Prof., Environ. Science
Center, Univ. of Tokyo, Japan
2008 - 2009
Visiting Assistant Prof., Drexel Univ., USA
1998 - 2008
Assist. Prof., Graduate School of Eng.,
Tohoku Univ., Japan
Research interests:- Quantitative microbial risk assessment (QMRA)- Development of mathematical model for QMRA
- Water-related infectious diseases

What is QMRA?

Water, air, soil,foods, etc.
Field investigation(Sampling & labanalysis)

Exposure
assessment
Fate of pathogens
andhuman behavior
Environmental
modeling &simulation

Risk estimation
Risk of infection

Microbial
contaminationin environment

ExposureCalculation withdose-responsemodel

Project on risk assessment of infectious disease
attributed to drinking water (2003-2006)
Investigated in rainy season
Investigated in dry season
Investigated in both seasons

Questionnaire survey

Lao PDR

Thailand

Detection of fecal indicator
bacteria in drinking water

Mekong River

Cambodia
VietnamDescription: Drinking water
Primary drinking water in the Mekong watershed
Area

Drinking water

Urban area

Tap water

Lao PDR
Rural area close (<1km) to rivers
Cambodia
Rural area away from rivers

River water
Well water

Urban area
VietnamThailandTap water

Rural area close (<1km) to rivers

River water, Rainwater

Rural area away from rivers

Well water, Rainwater

Urban area

Tap water, Bottled water

Rural area

Rainwater

VietnamThailandDescription: Contamination of drinking water (1)Estimation of fecal contamination of drinking water in Lao PDR,
Cambodia and Vietnam by multiple regression analysis
Dependent variables:

Mean concentrations of total coliforms in tap, well,river and rain water in each province

Independent variables: Provincial population, population density, ruralpopulation, poverty rate, access to safe drinking waterand access to adequate sanitation

Description: Contamination of drinking water (2)Significant regression equations were obtained for…
In rainy season
Well water: C = 0.93PD + 0.57WT – 1.4SN + 41
(R2 = 0.69, p = 0.01)
Rainwater:
C = 0.36RR – 0.81PV – 0.31WT – 0.25SN + 49
(R2 = 0.74, p = 0.02)
In dry season
Well water: C = 0.73WT – 0.57SN + 13
(R2 = 0.58, p = 0.08)
River water: C = 0.86PD + 20
(R2 = 0.70, p = 0.006)
Rainwater:
C = – 0.99PV + 172(R2 = 0.98, p = 0.07)
where, C: Concentration of total coliforms [CFU/mL]
PD: Population density [/km2]
Data from GIS (1km grid)
RR: Rural population [%]PV: Poverty rate [%]WT: Access to safe drinking water [%]SN: Access to adequate sanitation [%]Results: Annual risk of infectious diarrhea
110km

10-1
10-2
Lao PDR

10-3
10-4
10-5
10-6

Vientiane

High population densityThailand
without access toadequate sanitation
Approx. 12 million cases ofAnnual risk: 0.1 to 1
diarrhea annually occur inthe whole watershed.
Water-supplied area(PWS system)
Annual risk: Approx. 10-4

Phnom Penh

Cambodia

10kmVietnam

Results: Scenarios for the risk reduction (1)Scenario 1: Expansion of water-supplied area and strict management oftap water quality in Lao PDR, Cambodia and Vietnam
Status quo

Case 1Case 2

Water-supplied population(Percent in the 3 countries)

3.2%

9.1%

13%

Total coliforms [CFU/mL]
in tap water (Rainy/Dry)

PWS: 1 / 12
VWS: 93 / 105

Annual risk of infectious
diarrhea around Vientiane,
Lao PDR

10-6

10-4

10-2

1

Annual cases of diarrhea

10km

PWS: 1 /VWS: 1 /1110km

10km

- 15%
10.7million

10.0 million

Vientiane

11.8 million

Results: Scenarios for the risk reduction (2)Scenario 2: Promotion of drinking rainwater in Lao PDR,
Cambodia and Vietnam
Total coliforms
Case 1: 5 provinces in each country
in rainwater

Case 3: All provinces (58 in total)

46 CFU/mL

Annual cases (million) of infectious diarrhea

Case 2: 10 provinces in each country

130 cm

12Status quo

Case 1Case 2- 72%

10863.4 million

420
Statusquo

Case 1Case 2 Case 3
10-6
10-4

10-21

Case 3

Water-related infectious diseases
Waterborne diseases
Are caused by pathogens that can be directly spread throughcontaminated water.
[Diarrhea, cholera, leptospirosis, shigellosis, typhoid fever, etc.]

Sanitation & hygiene-related diseases
Could be prevented through better access to adequate sanitation
facilities (e.g. toilet and latrines) and better hygiene practices (e.g.
frequent hand-washing, face washing, and bathing with soap andclean water).
[Scabies, ringworm, trachoma, etc.]

Vector or insect-borne diseases associated with water
Are spread by insects, such as mosquitos, breeding around water.
[Dengue fever, malaria, yellow fever, etc.]

Climate change and water-related
infectious diseases
Climate change
Rise in temperature

Expansion ofvectors’ habitatfrom tropical totemperate regions

Risk of vectorborne diseases
associated withwater

Change in rainfalls

Enhancementof pathogens’
growth in water

Frequent
occurrence offlood & drought

Difficulty to access to safe drinking
water and adequate sanitation
Risks of waterborne, sanitationand hygiene-related diseases

Freshwater availability in 2007

Change in water availability

Large flood events (1985-2007)

Change in frequency of flood eventsfrom 1993 to 2003

Source: NIES, Japan>100% increase<90% increase
Newly occurred
Same<49% decrease>50% decrease
No floodRisk of waterborne diseases
during flood events
Flood water is probably contaminated by overflow from canals
receiving domestic and industrial wastewater.
Risk of waterborne diseases would increase due to exposure
to such a contaminated flood water.

Combined sewer system as“underground canal network”.

Life during flood in Hue, Vietnam

Moving furniture

Going to shops
or work places

Cooking

Swimming &playing

Estimated risk of illness causedby E.coli in water
Risk during flood events(only for 6.5 days)

Risk in normal time
(calculated for 365 days)-4
Scenario
Risk* (x10 )Moving furniture & cleaning
2822
Cooking1433
Playing916
Going shopping
751
Going to work
322
Eating raw vegetables at165
home
Swimming
13
Drinking ice at home
0.0001
Total risk in flood time
4496
*Estimated using averages of interview data
(n=989).

-4
Scenario
Risk* (x10 )Eating raw vegetables
177
at homeEating raw vegetables
59
at shop
Fishing
15
Swimming
9
Drinking ice at shop
0.4
Drinking ice at home
0.2
Total risk in normal time
258
*Estimated using averages ofinterview data (n=989).

Leptospirosis: a waterborne
zoonotic disease
Ingestion ofcontaminatedwater

Living in (infecting to)kidney of animals

Excreted with urine

Invasion through skin

Photo from National Institute of Infectious Disease, Japan

This report is available at http://www.irinnews.org/report.aspx?ReportId=86779

Risk of leptospirosis depending on
number of invading cells
10.9

Risk of leptospirosis

0.8
0.7

Dense population of mice
especially in urban environment(e.g. sewer system)

0.6
0.50.4

Risk of cut on legs when
walking in muddy flooded area

0.30.2

Lepto can easily invade humanbody through such a cut

0.1
00.1

1101001000

10000 100000

Number of cells invading human bodyRisk of water-related infectious
diseases during drought
Waterborne diseases
Are caused by pathogens that can be directly spread throughcontaminated water.
[Diarrhea, cholera, leptospirosis, shigellosis, typhoid fever, etc.]

Sanitation & hygiene-related diseases
Could be prevented through better access to adequate sanitation
facilities (e.g. toilet and latrines) and better hygiene practices (e.g.
frequent hand-washing, face washing, and bathing with soap andclean water).
[Scabies, ringworm, trachoma, etc.]

Vector or insect-borne diseases associated with water
Are spread by insects, such as mosquitos, breeding around water.
[Dengue fever, malaria, yellow fever, etc.]
ScabiesTrachoma

Cholera outbreak in Haiti after
earthquake in January 2010

Schistosomiasis: a waterborne andneglected tropical disease
Egg

Snail: Intermediate hostMiracidium(1st stage)

Cercaria(2nd stage)

Adult worm living
in portal vein

Summary
Occurrence frequencies of flood and drought seem tobe globally increasing probably due to climate change.
Flood and drought pose a higher risk of water-relateddiseases, such as diarrhea, leptospirosis andschistosomiasis, than normal time due to a frequentcontact to contaminated water.
QMRA could help us understand whether or notoutbreak of infectious diseases happens during floodand drought, where it dose, how large it is, and also
how many cases of infectious diseases can be
reduced with supposed countermeasures against
flood and drought.