Climate change and health effect

1
Climate change and health effect

• Lokman Hakim S,
• MD, DAPE, MScPH, PhD, FAMM
• Environmental Health Research Centre,
• Institute for Medical Research,
• Kuala Lumpur

2
Recent and projected climate change

• United Nation Intergovernmental Panel on Climate
  Change increasing evidence of recent warming
• Since 1950s
• Global average surface temperature increased by
  0.6oC
• Snow cover and ice extent diminished
• Increased ocean temperature
• Mid-range estimates by 2100
• 3oC global mean warming
• A rise of 45cm in sea level

3
Global events

• 1998
• Hurricane Mitch dropped 6 feet of rain in Central
  America
• Increased incidence of malaria, dengue, cholera
  leptospirosis
• 1999
• Cyclone Orissa caused 10,000 death 10-15
  million affected
• Flood in Caracas, Venezuela killing 30,000 people
• 2000
• Rain and hurricane inundated Mozambique, causing
  malaria incidence to increase 5 folds
• 2003
• Summer heat wave in Europe killing thousands of
  people (27,000 more death in corresponding period
  the previous year, massive forest fires and
  melting 10 of the Alps ice.

4
Recent Climate-Related Extreme Events 2005

• Unprecedented blistering summer heat
• More than 200 cities with new record for high
  temperature
• Sustained temperature of gt38oC for 39 consecutive
  days, including a week above 43oC in Phoenix,
  Arizona
• Hurricane Catrina, Rita and Wilma

5
Climate change and health pathway from driving
forces, through exposures to potential health
impact.
Source Climate Change and Human Health Risks
and Reponses. Summary (WHO, 2003)
6
Four main types of transmission cycle for
infectious diseases
Source Climate Change and Human Health Risks
and Reponses. Summary (WHO, 2003)
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Biologic response to changes in climate

• Global warming and wider fluctuation in weather
  help to spread diseases
• Temperatures affect growth, development and
  survival of microbes and the vectors
• Weather affects the timing and intensity of
  disease outbreaks (McMichael et al, 2003)

8
Biologic response to changes in climate
Infectious diseases

• Warmer environment and mosquitoes
• Boost rate of reproduction
• Increase the number of blood meal
• Prolongs their breeding season
• Shorten the maturation period of microbes they
  carry
• Warmer winters tick-borne lyme disease
  spreading northward in Sweden, US and Canada
  (Epstein, 2005)
• Heavy downpours
• Drive rodents from burrows risk of zoonotic
  diseases
• Create mosquito breeding sites
• Faster fungal growth in houses
• Flush pathogens and chemicals into waterways
• Milwaukees cryptosporidiosis outbreak in 1993
• Katrinas flood water-borne pathogens and toxins
  spread.

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Using climate to predict infectious disease
outbreaks

• Generally accepted that climate plays a role in
  infectious disease transmission
• Considerable on-going research activity
  identifying climate-epidemic links
• Many research projects have demonstrated temporal
  link between climatic factors and variations in
  disease rates
• Some are able to predict epidemics but the tests
  are very preliminary and based on limited data

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Little evidence to suggest that any of these
systems are being used to influence disease
control decisions

• Affordability and accessibility of data and
  analytical tools
• No generally agreed criteria for assessing
  predictive accuracy
• Not tested in locations outside the study area
• Most studies focus on climatic factors only

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Climate and infectious diseases in Malaysia
early warning system? study approach

• Focus on infectious diseases
• WHO conceptual framework climate-based Early
  Warning System
• Review trends in incidence of those diseases
  associated with climate
• Access of availability and quality of data
• Developing and testing the model

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Conceptual framework for developing climate-based
Early Warning System (EWS) for infectious disease
(WHO, 2004)

• Evaluating epidemic/outbreak potential
• Seasonal fluctuation
• Geographical localisation of outbreak
• Risk of epidemic not equal in all locations
• Identifying climatic and non-climatic risk
  factors
• Risk assessment
• Non climatic factors immunity level, nutrition,
  drug insecticide resistance
• Quantifying climate variability-outbreak link
  Predictive model

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Conceptual framework for developing climate-based
Early Warning System (EWS) for infectious disease
(WHO, 2004)

• Evaluating epidemic/outbreak potential
• Geographical localisation of outbreak
• Identifying climatic and non-climatic risk
  factors
• Quantifying climate variability-outbreak link
  Predictive model
• Availability of both disease and explanatory data
  at appropriate spatial temporal resolutions and
  for a sufficient time-frame
• Climate data
• Direct, ground based measurement limited
  representation
• Surrogate measures from remote sensing
  accessibility

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Infection Climate Potential endemic diseases
in Malaysia
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Food and water-borne diseases
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Incidence of vector-borne diseases per 100,000
population Dengue and malaria
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Temperature, vectorial capacity of Ann. maculatus
and projected number of malaria cases (Ambu et
al. 2003)
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Incidence of malaria per 100,000 population
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Malaria in Tawau, Sabah
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Epidemic in Air Bah Lubok Cupak, Perak Field
observation
No. of Cases
Plantation clearing for replanting completed
1999
2000
2001
Hakim SL et al. (2002)
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Felda Neram, Terengganu Epidemic, 2000
No. of cases
weeks
Hakim SL et al, (2001)
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Incidence of dengue per 100,000 population
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Rainfall and dengue outbreak in Malaysia

• Modification of Mogi et al. 1990 model
• Study the threshold of rainfall actually required
  to trigger an outbreak
• Dengue incidence and rainfall data in 1986-1997
• Model indicated relatively fewer raining days are
  required for high transmission
• Heavy rain flushes off breeding habitats

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New model incorporating mosquito vectorial
capacity into the regression model

• Multiple regression model
• Rainfall, temperature, humidity and vectorial
  capacity
• Vectorial capacity (Vc) the mean of potentially
  infective contacts by a mosquito population per
  infectious person per time
• Vc m b c a2 Pn
• -Ln(P)
• a number of bites per human per day
• b probability that an infectious mosquito
  transmit dengue while biting a susceptible human
• c probability that a mosquito acquires a dengue
  infection while biting a viremic human
• m number of female mosquitoes per person
• n duration of extrinsic incubation period (time
  required for the virus to disseminate throughout
  the mosquito
• P survival of mosquito
• Temperature high increase in biting rate,
  incubation period and survival -gt increase in
  vectorial capacity
• Complexity affect practicality

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Problem encountered

• Data availability
• Climatic parameters not available for all
  stations
• Setapak station No temperature humidity data
• Incomplete dengue data, available only for the
  last 7 years (1997-2004)
• Data mining manual key-in from hard copy
  (1997-2001)
• Data quality
• Many missing data 40 of the epidemiological
  week for 1997 and 1998
• Double entry and wrong zoning of dengue cases
• Differences in diagnostic methods and reporting
  system

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Is climate change a serious threat to health?

• The threat is unquestionable
• However, the impact depends on-
• Where you live
• Your age
• Access to health care
• Public health infrastructure
• Adverse effects will generally occur in poor
  populations that have little capacity to adapt

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Maximum and maximum temperature Station No.
44333
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Climate change and health impact

• Impact on infectious diseases transmission may
  not be so obvious in Malaysia
• Very good health infrastructure
• Very good accessibility to HC
• Effective adaptation measures
• Vector-control programme
• Immunization programme
• Safe water and sanitation
• Food safety hygiene
• Improving socio-economic status
• Increasing inter-sectorial cooperation and
  collaboration
• Challenges to scientist complex nature of causal
  process, unavoidable uncertainties
• More research into adaptation measures
• Improvement in disease surveillance preparedness

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Climate change and health pathway from driving
forces, through exposures to potential health
impact.
Source Climate Change and Human Health Risks
and Reponses. Summary (WHO, 2003)
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Early warning system preparedness

• Most of the extreme climatic changes (e.g. heat
  wave, torrential rain, hurricane) can be
  predicted several days in advance
• But how prepared are we to deal with the
  situation?
• National Centre for Communicable Diseases (NCCD)

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Acknowledgement

• Ministry of Environment and Natural Resources
• Dewan Badaraya Kuala Lumpur
• Universiti Teknologi Mara
• Disease Control Division, MOH
• Infectious Disease Research Centre, IMR
• Environmental Health Research Centre, IMR