managing the changing health risks of climate change

Available online at www.sciencedirect.com

Managing the changing health risks of climate changeKristie L Ebi

Climate change will make the control of many climate-sensitive

health determinants and outcomes more difficult. Because the

health determinants and outcomes that are projected to

increase with climate change are problems today, in most

cases the primary response will be to enhance current health

risk management activities. However, that is unlikely to be

sufficient to address changing disease patterns and new health

risks. Health policies and programs need to explicitly

incorporate current and projected climate-related risks in order

to maintain and enhance current levels of control.

Addresses

IPCC WGII TSU, c/o Carnegie Institution of Science, 260 Panama Street,

Stanford, CA 94305, USA

Corresponding author: Ebi, Kristie L ([email protected])

Current Opinion in Environmental Sustainability 2009, 1:107–110

This review comes from the inaugural issues

Edited by Rik Leemans and Anand Patwardhan

Available online 21st August 2009

1877-3435/$ – see front matter

# 2009 Elsevier B.V. All rights reserved.

DOI 10.1016/j.cosust.2009.07.011

IntroductionA key conclusion from the Synthesis Report of the

Intergovernmental Panel on Climate Change Fourth

Assessment Report was [1]:

Responding to climate change involves an iterative risk

management process that includes both adaptation and

mitigation and takes into account actual and avoided

climate change damages, co-benefits, sustainability,

equity, and attitudes to risk.

It was further noted that application of risk management

requires knowledge not only of projections of the most

likely climate scenarios, but also of lower probability and

higher consequences events. Climate change impacts

depend on the extent and magnitude of climate change,

as well as on the characteristics of natural and human

systems, their development pathways, and their specific

locations.

With more than 150 years of experience in primarily

successful control of acute and chronic health risks,

public health should be well placed to address the

additional health risks due to climate change. The

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main concerns worldwide are that climate change

could increase the geographic range and/or incidence

of malnutrition, diarrheal disease, and malaria [2�];these are leading causes of childhood morbidity and

mortality. Diarrheal diseases claim the lives of nearly

two million children annually, with most of the deaths

attributable to contaminated water, and inadequate

sanitation and hygiene [3]. Annually, approximately

300–500 million malaria infections lead to over one

million deaths, 75% of which occur in African children

under five years of age. Malnutrition remains an under-

lying cause of death of half of the 10.5 million deaths

globally in children under age five. About 50% of

maternal and childhood underweight is a consequence

of inadequate water and sanitation provisions and

hygienic practices, leading to repeated infections,

especially diarrheal episodes that affect subsequent

mortality. When all the effects of malnutrition are

considered (including loss of cognitive function, poor

school performance, and loss of future earning poten-

tial), the total estimated costs could be as high as 8–9%

of a typical developing country’s GDP in South Asia or

sub-Saharan Africa [3].

There are known, effective public health responses to

monitor and control the burden of these and other

climate-sensitive health outcomes [4�,5�,6�]. The World

Health Organization, Ministries of Health, nongovern-

mental organizations such as the International Federa-

tion of Red Cross/Red Crescent Societies, the World

Bank, bilaterals, international funders and donors, and

many others have programs designed to monitor and

reduce current health burdens. Strengthening current

health protection would not only save lives, but would

increase the capacity to address any additional risks due

to climate change [7]; a win–win opportunity.

However, public health and health care strategies,

policies, and measures were designed assuming that

climate is basically constant. Increasing climate variability

and change is projected to increase the geographic range

and incidence of climate-sensitive health outcomes [2�].If realized, these changes will likely challenge the ability

of programs and activities to maintain current levels of

control. Malaria is used to illustrate that focusing solely on

strengthening current health protection is unlikely to be

sufficient to maintain current levels of control with chan-

ging disease distributions, and that climate change may

decrease the skill of early warning systems. An outbreak

of Vibrio parahaemolyticus in Alaska is used to illustrate

some of the challenges of preparing for the emergence of

infectious diseases.


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http://dx.doi.org/10.1016/j.cosust.2009.07.011

108 Inaugural issues

Changing disease distributionsClimate is one determinant of whether a particular

location has the environmental conditions suitable for

the transmission of a wide range of infectious diseases.

Increasing temperatures and changes in the hydrologic

cycle are providing opportunities for a range of pathogens

and vectors to change their geographic range, replication

rate, and transmission dynamics. In particular, there is

considerable interest in how climate change could affect

the geographic range and incidence of malaria. Projec-

tions suggest that climate change will be associated with

geographic expansions of the areas suitable for stable

Plasmodium falciparum malaria in some regions and with

contractions in others by altering conditions conducive for

the survival of the vector (Anopheles) and pathogen (Plas-modium) along the edges of their current distribution [2�].Most projections do not consider how effective vector and

disease control programs could decrease the impact of

changes in malaria’s future incidence and geographic

range.

Malaria is the most important vectorborne disease in the

world; it is also a preventable disease. It places significant

burdens on families and communities, particularly in

Africa where 80% of all cases and 90% of mortality occur

[8,9]. In sub-Saharan Africa, malaria remains the most

common parasitic disease and is the main cause of mor-

bidity and mortality among children less than five years of

age and among pregnant women [10].

Malaria has proved difficult to control [11]. Despite

larviciding, insecticide residual spraying, chemoprophy-

laxis for particularly vulnerable groups (i.e. pregnant

women and children), and effective case management,

there has been a global resurgence of epidemic malaria

over the past two decades, causing significant morbidity

and mortality. Reasons suggested for the resurgence

include failure of malaria control programs, population

redistribution and growth, changes in land use, increasing

prevalence of drug and pesticide resistance, degradation

of public health infrastructure, and climate variability and

change [12,13]. These and other determinants of malaria

often act jointly with positive feedbacks that increase

malaria transmission [14]. Therefore, the severity of

malaria is a function of interactions among the malaria

parasite, the mosquito vector, the host, and the environ-

ment.

The vectors that carry malaria require specific habitats,

with surface water for reproduction, and favorable tem-

peratures and humidity for adult mosquito survival.

Numerous laboratory and field studies have documented

that a change in temperature may lengthen or shorten the

season during which mosquitoes or parasites can survive;

and that changes in precipitation or temperature may

result in conditions during the season of transmission

that are conducive to increased or decreased parasite


and vector populations. At warmer temperatures, adult

female mosquitoes feed more frequently and digest blood

more rapidly, and the Plasmodium parasite matures more

rapidly within the female mosquitoes. Temperature also

affects the duration of the aquatic stage. Small changes in

precipitation or temperature may allow transmission in

previously inhospitable altitudes or ecosystems.

Most malaria epidemics follow abnormal weather con-

ditions, often in combination with other causes [15,16].

Epidemic malaria is a serious problem in semi-arid and

highland areas (above 2000 m) in eastern and southern

parts of Africa. Reports suggest that the incidence of

malaria in the East African highlands has increased since

the end of the 1970s [11]. Analysis of temperature data

from 1950 to 2002 for four high-altitude sites found

evidence for a significant warming trend [17]. The

possible biological significance of this trend was assessed

using a model of the population dynamics of the mosquito

vectors for malaria and concluded that the observed

temperature changes could significantly accelerate the

mosquito life cycle, particularly the development rate of

larvae and adult survival. Even a small increase in

temperature may result in a significant increase in the

number of available malaria vectors. Because the prob-

ability that an Anopheles mosquito will transmit malaria

with each bite is low, the number of available competent

vectors is an important determinant of an epidemic.

The consequences of epidemic malaria can be severe.

When population immunity is low, significant morbidity

and mortality can occur in children and adults. Case

fatality rates can be up to 10-times greater during an

epidemic [16]. Malaria among older, more productive

members of the community amplifies the impacts of

the epidemic on families and society. It is estimated that

epidemic malaria causes 12–25% of estimated annual

worldwide malaria deaths, including up to 50% of the

estimated annual malaria mortality in persons less than 15

years of age [18].

Controlling malaria epidemics is problematic today.

Focusing only on improving surveillance and control

programs in current locations is not designed to detect

the emergence of malaria in new regions. Current con-

trol programs could be augmented to consider how

climate change could affect the present situation using

expert judgment, adding surveillance sites in suscept-

ible locations, and modeling where and when the vector

and pathogen might change their geographic ranges.

Although there are large uncertainties with modeling

a disease as complex as malaria, not designing and

employing such models for use at national and district

levels often means waiting for epidemics to occur, with

consequent preventable morbidity and mortality. It will

be challenging to determine where and when to close

down surveillance programs in regions where a disease


Managing climate change health risks Ebi 109

no longer occurs and to open new programs before

epidemics arise. Explicit criteria are needed for decid-

ing when to close/open surveillance sites in areas where

malaria is expected to decrease/increase in intensity,

taking into account climate change and other major

disease determinants. Actively incorporating ongoing

climate change risks into surveillance and control pro-

grams, with sufficient public health intervention capa-

bilities, is essential for countering current and future

threats from malaria and other vectorborne diseases.

Achieving this can be facilitated by running a range

of climate change projections through a malaria model

to project where and by when malaria could change its

geographic range and/or the length of the season could

alter in a particular region; this information could then

be used in conjunction with expert opinion to determine

when and where the location of activities should be

changed.

Early warning systemsBecause current surveillance is not able to provide timely

detection of the onset of epidemics in many at-risk areas,

there is increased interest in using remotely sensed

environmental variables that indicate conditions condu-

cive for an outbreak. Early warning systems can save lives

when they intensify vector control activities and increase

the reserve capacity in insecticide-treated bednets, anti-

malarial drugs, etc. [19]. However, increased climate

variability may make early warning systems based on

these variables more unreliable.

Hay et al. [20] assessed whether a combination of seasonal

climate forecasts, monitoring of meteorological con-

ditions, and early detection of cases could have helped

prevent the 2002 malaria emergency in highland regions

of western Kenya. Seasonal climate forecasts did not

anticipate the heavy rainfall. On a shorter time scale,

rainfall data gave timely and reliable early warnings.

However, normal rainfall conditions in two regions led

to typical outbreaks, while exceptional rainfall in two

other regions led to epidemics. Routine health infor-

mation and management systems did not give timely

warning of the epidemic. Similar conclusions were

reached in studies in Tanzania [21] and Eritrea [22].

Jones et al. [21] concluded that the underlying relation-

ship between rainfall and malaria in their study district

was too complicated to analyze using regression analysis.

Ceccato et al. [22] found that although correlations in 58

districts were good between malaria anomalies and

measured rainfall, the weather stations did not have

sufficient coverage to be widely useful and the seasonal

forecasting skill was low for the June/July/August rains,

except for one region.

Projections of increased climate variability [1] suggest

that the design of early warning systems should consider

how to incorporate changing baselines, increases in cli-


mate variability, and additional evaluation so that modi-

fications can be implemented proactively.

Emerging diseasesClimate change may facilitate the emergence of unanti-

cipated infectious disease. For example, V. parahaemoly-ticus, the leading cause of seafood-associated

gastroenteritis in the US, is typically associated with

the consumption of raw oysters gathered from warm-

water estuaries. In 2004, an outbreak occurred in Alaska

where the consumption of raw oysters was the only

significant predictor of illness; the attack rate among

people who consumed oysters was 29% [23]. All oysters

associated with the outbreak were harvested when mean

daily water temperatures exceeded 15.08C (the theorized

threshold for the risk of V. parahaemolyticus illness from

the consumption of raw oysters). Between 1997 and 2004,

mean water temperatures in July and August at the

implicated oyster farm increased 0.218C per year; 2004

was the only year during which mean daily temperatures

did not drop below 15.08C. The outbreak extended by

1000 km the northernmost documented source of oysters

that caused illness due to V. parahaemolyticus. Rising

temperatures of ocean water appear to have contributed

to one of the largest known outbreaks of V. parahaemo-lyticus in the US.

This example illustrates the challenge of anticipatory

adaptation. It would have been difficult for a state or

national health department to anticipate the outbreak of

a disease whose previous geographic limits were so dis-

tant. A key approach to prepare for unanticipated risks is

to develop models of climate-sensitive health outcomes

that include the major drivers of disease emergence, to

develop a better understanding of the required con-

ditions for diseases to appear in new areas. One challenge

will be that model projections, even robust results, could

be ignored if the changes projected are outside the

experience of the (potentially) affected societies (com-

munities, regions, and nations). Taking effective action

based on model projections and expert knowledge will

require increased understanding of climate change and

associated health risks by all stakeholders, the strengths

and uncertainties associated with model projections, and

the likely financial and human consequences of action

and of inaction.

ConclusionsUrgent and immediate actions are needed to prepare for

and effectively respond to the health risks of climate. In

addition to enhancing current health protection pro-

grams, public health agencies, and institutions need to

develop the capacity to identify and attribute changing

disease patterns to climate change, and use climate

projections to indicate where (and which) health out-

comes would likely change under different climate

scenarios.


110 Inaugural issues

It is critical that adaptation strategies, policies, and

measures are not only effective and efficient today, but

also flexible to allow for modifications as more is under-

stood of where and when climate change may alter the

geographic distribution and incidence of climate-sensi-

tive health outcomes. Achieving this dual focus on current

and projected future health risks of climate change is a

cornerstone for effective iterative risk management.

References and recommended readingPapers of particular interest, published within the period of review, hasbeen highlighted as:

� of special interest�� of outstanding interest

1. Intergovernmental Panel on Climate Change (IPCC): In SynthesisReport: Contribution of Working Groups I, II and III to the FourthAssessment Report of the Intergovernmental Panel on ClimateChange. Edited by Core Writing Team, Pachauri RK, Reisinger A.Geneva, Switzerland: IPCC; 2007:104.

This reference synthesizes the conclusions of Working Group I (thephysical science basis), Working Group II (impacts, adaptation, andvulnerability), and Working Group III (mitigation of climate change) ofthe Intergovernmental Panel on Climate Change.

2.�

Confalonieri U, Menne B, Akhtar R, Ebi KL, Hauengue M,Kovats RS, Revich B, Woodward A: In Human Health. ClimateChange 2007: Impacts, Adaptation and Vulnerability. Contributionof Working Group II to the Fourth Assessment Report of theIntergovernmental Panel on Climate Change. Edited by Parry ML,Canziani OF, Palutikof JP, van der Linden PJ, Hansson CE.Cambridge, UK: Cambridge University Press; 2007.

This chapter of the Intergovernmental Panel on Climate Change 4thAssessment Report assessing current knowledge of the human healthimpacts of and public health adaptation to climate change.

3. World Bank: Environmental Health and Child Survival;Epidemiology, Economics, Experiences. Economic and HealthSector, Environment Department; 2008.

This volume details the substantial health burdens and consequenteconomic costs of malnutrition, poor environmental conditions, andinfectious diseases on children in the developing world.

4.�

Ebi KL: Public health responses to the risks of climatevariability and change in the United States. J Occup EnvironMed 2009, 51:4-12.

This publication discusses the capacity of the United States to adapt tothe potential impacts of environmental change, including the concept ofadaptation to climate change as risk management; identifies the mainactors involved in public health responses to climate change, includingtheir roles and responsibilities in adaptation; and lists the general types ofadaptation measures to manage health risks related to climate change,and give examples of measures for specific effects of climate change.

5.�

Frumkin H, Hess J, Luber G, Malilay J, McGeehin: Climatechange: the public health response. Am J Public Health 2008,98:435-445.

This publication proposes a public health approach to climate change,based on the essential public health services, that extends to both clinicaland population health services and emphasizes the coordination ofgovernment agencies (federal, state, and local), academia, the privatesector, and nongovernmental organizations.

6.�

Keim ME: Building human resilience: the role of public healthpreparedness and response as an adaptation to climatechange. Am J Prev Med 2008, 35:508-516.


This publication discusses the role of public health in reducing humanvulnerability to climate change within the context of selected examples foremergency preparedness and response.

7. McMichael AJ, Neira M, Heymann DL: World Health Assembly2008: climate change and health. Lancet 2008,371(19628):1895-1896.

8. Breman J: The ears of a hippopotamus: manifestation,determinants and estimates of the burden. Am J Trop Med Hyg2001, 64:1-11.

9. D’Alessandro U, Buttiens H: History and importance ofantimalaria drug resistance. Trop Med Int Health 2001, 6:845-848.

10. WHO: Malaria Epidemics: Forecasting, Prevention, Early Warningand Control — From Policy to Practice Geneva: World HealthOrganization; 2004.

11. Githeko AK, Shiff C: The history of malaria control in Africa:lessons learned and future perspectives. In Integration ofPublic Health with Adaptation to Climate Change: Lessons Learnedand New Directions. Edited by Ebi KL, Smith J, Burton I. London:Taylor & Francis; 2005:114-135.

12. Githeko AK, Ndegwa W: Predicting malaria epidemics usingclimate data in Kenyan highlands: a tool for decision makers.Global Change Human Health 2001, 2:54-63.

13. Greenwood B, Mutabingwa T: Malaria in 2002. Nature 2002,415:67-672.

14. Janssen M, Martens P: Modelling malaria as a complexadaptive system. Artificial Life 1997, 3:213-236.

15. Abeku TA: Response to malaria epidemics in Africa. EmergInfect Dis 2007, 13:681-686.

16. Kiszewski AE, Teklehaimanot A: A review of the clinical andepidemiologic burdens of epidemic malaria. Am J Trop MedHyg 2004, 71(Suppl 2):128-135.

17. Pascual M, Ahumada JA, Chabes LF, Rodo X, Bouma M: Malariaresurgence in the East African highlands: temperature trendsrevisited. Proc Natl Acad Sci U S A 2006, 103(15):5829-5834.

18. Worrall E, Rietveld A, Delacollette C: The burden of malariaepidemics and cost-effectiveness of interventions in epidemicsituations inAfrica.AmJTropMed Hyg 2004,71(Suppl2):136-140.

19. Thomson MC, Doblas-Reyes FJ, Mason SJ, Hagedorn R,Connor SJ, Phindela T, Morse AP, Palmer TN: Malaria earlywarnings based on seasonal climate forecasts from multi-model ensembles. Nature 2006, 439:576-579.

20. Hay SI, Were EC, Renshaw M, Noor AM, Ochola SA, Olusanmi I,Alipui N, Snow RW: Forecasting, warning, and detection ofmalaria epidemics: a case study. Lancet 2003, 361:1705-1706.

21. Jones AE, Uddenfeldt Wort U, Morse AP, Hastings IM, Gagnon AS:Climate predictions of El Nino malaria epidemics in north-westTanzania. Malaria J 2007, 6:162 doi: 10.1186/1475-2875-6-162.

22. Ceccato P, Ghebremeskel T, Jaiteh M, Graves PM, Levy M,Ghebreselassie S, Ogbamariam A, Barnston AG, Bell M, delCorral J et al.: Malaria stratification, climate, and epidemicearly warning in Eritrea. Am J Trop Med Hyg 2007, 77(6Suppl):61-68.

23. McLaughlin JB, DePaola A, Bopp CA, Martinek KA, Napolilli NP,Allison CG, Murray SL, Thompson EC, Bird MM, Middaugh JP:Outbreak of Vibrio parahaemolyticus gastroenteritisassociated with Alaskan oysters. N Engl J Med 2005, 353:1463-1470.


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managing the changing health risks of climate change

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