Isaac Rowner
Profs. Simms and Temeles
10/20/10
Enst 70
Climate Change and Health: Effects of Infectious Disease
I.
Effects of climate change on health- overview
a. Evidence of climate change
i. General climate change scenarios
b. Direct vs. indirect effects of climate change
i. Direct effects of increased temperature such as deaths due to heat
waves are much more evident than complex interactions that cause
indirect effects such as those on infectious disease and malnutrition
due to crop failure.
c. Vulnerable areas
i. Temperate regions, El Ni̐ ño/Southern Oscillation, “heat island”
effect
d. Regions with greatest burden of climate-sensitive diseases are those with
lowest capacity to adapt to new risks
II.
Infectious disease as a point of further investigation
a. Climatic variations could have profound impact
i. Survival, development, replication, and activity of both infectious
agents and vector organisms could be strongly effected due to lack
of thermostatic mechanisms
b. Malaria as a point of analysis
i. Potential to be significantly impacted by climate change
ii. Major public health burden in the tropics
iii. Incidence has escalated in the last two decades
iv. Priority for global development by intergovernmental institutions
III.
Will climate change increase incidence of infectious diseases such as malaria?
a. General prediction of increased incidence due to media attention and
popular concern, but highly debated
i. Infectious diseases are complex and can be affected by a variety of
factors
b. Three main criticisms to general prediction in recent literature
i. Disease could shift geographically without a net increase in
incidence
1. Specific parasites and vectors have optimal temperature
ranges
2. Climate change could cause decline in populations by
moving out of optimal temperature ranges
ii. Non-climatic factors are more important than climate
1. It’s clear that non-climatic factors are important, but can
rule out climate as major contributing factor?
iii. To predict increasing disease transmission models must show that
transmission rate exceeds a specific threshold (R0 >1)
1. Historical records of the distribution of malaria include
large geographical areas in which the projected values of
R0 were less than one
2. If the initial outbreak is caused by the simultaneous arrival
of a large number of infected hosts disease could still
invade
IV.
Projections of future malaria prevalence due to climate change
a. Rogers and Randolph (2000)
i. “medium-high” climate scenario predicted 23 million additional
people living in malarious areas, while “high” scenario predicted
25 million fewer people
ii. Fragility of the relationships between parasite and vectors and
climatic conditions
iii. Statistical versus biological models
b. Tanser et al. 2003
i. Using different climate change scenarios estimated a 5-7%
potential increase in malaria distribution due to a prolonged
transmission season
ii. Estimated that a large proportion of increased distribution will be
seen in areas of existing transmission and will be mainly altitudinal
c. Pascual et al. (2006)
i. Analyzed a long term data set of four East African Highland sites
where there has been a marked resurgence of malaria and showed a
significant warming trend at all four sites
ii. Using a dynamical model they also found that even small changes
in the climate signal can dramatically amplify mosquito abundance
1. Significant public health implications for spread of disease
to new regions
d. Lieshout et al.
i. Used different climate change scenarios to find that in East Africa,
central Asia, and areas around the southern limit of the distribution
in South America there will be additional populations at risk of
contracting malaria
ii. Employed a new method of for describing vulnerability according
to current vulnerability and malaria control status and estimated
that in countries that currently have a limited capacity to control
the disease will have additional populations at risk by the 2080s.
V.
Economic and social costs of climate change on health
a. Effects are generally externalities that are unprecedentedly large, complex,
and uncertain
b. Costs
1. DALYs,
2. Disproportionate effect on youngest generation
c. Models to estimate costs
d. Link between economic and social costs
i. Cyclical- increased prevalence leads to decreased economic
productivity leads to increased inability to address problem
VI.
What can we do? – possible solutions
a. Most likely best approach is to attack each issue individually
i. Coordinate anti-malarial programs in the most vulnerable regions
including those where there is a predicted potential increase in
transmission
ii. Push forward policy initiatives to mitigate emissions of greenhouse
gases
VII.
Policy initiatives
a. The Intergovernmental Panel on Climate Change comprised of top climate
scientists from around the globe has reached a consensus that human
activities have contributed significantly to global climate change
i. The United States has refused to join concerted international
efforts, such as the Kyoto protocol to curb human activities
contributing to climate change
ii. Policy responses so far have had little or no impact on the buildup
of emissions.
b. Consistent adherence to interacting journalistic norms has contributed to
barriers in the coverage of anthropogenic climate change science (Boykoff
and Boykoff 2007)
c. Framing of issue
i. Possibly presenting more evidence of direct human effects of
climate change will spur public action