Pilot Project for Predicting and Mitigating an Outbreak of Dengue

Fever – Capacity Building and Learning Experience Based on SIS06

A.Anthony Chen, Climate Studies Group Mona,

Department of Physics, UWI, Mona

The Dengue-Climate Problem

The water problem:

•In times of rain, pools of water collect in discarded coconut shells, automobile tyres and other nonbiodegradable containers providing breeding habitats.

The water storage problem:

•In dry periods, water is stored in open containers which provide breeding habitats

The Temperature Problem:•The extrinsic incubation period (period of incubation of parasite inside the vector or EIP) shortens at higher temperature

•Focks et al (1995) - dengue type 2 has an EIP of 12 days at 30○ C but only 7 days at 32-35○ C. •Koopman et al. (1991) - decreasing the incubation period by 5 days can lead to a threefold higher transmission rate of dengue.

•Higher temperatures increase the amount of feeding and the probability of dengue transmission to new hosts.

•Moderately high temperatures hasten the larval stage, leading to smaller mosquitoes, which then require more frequent blood meal.•Increased temperature also enhance metabolism.

The El Nino Problem:•Taylor (1999) - El Niño years in the Caribbean produce drier than normal conditions in the latter half of the year• This drying tendancy was also reported by others, including Ropelewski and Halpart (1996)

The above leads to the storing of water problem •The air temperature increases during El Niño conditions in the Caribbean (Malmgren et al, 1998).

This leads to the temperature problem. •Chen et al (1997), Taylor (1999), Chen and Taylor (2001) showed how rainfall increases during May to July in the El Niño + 1 year

This leads to the water problem.

The Climate Change Problem:

•Santer (2001) found that a mean temperature increase of up to 2ºC is projected for Caribbean after 70 years of CO2 doubling.

•Expected modulation of temperature by future El Niño events will further enhance above increase periodically.

• Timmermann et al (1999) found an increase in El Niño frequency in a climate model forced by future greenhouse warming.

All the above lead to the temperature problem

•IPCC (1998), based on 1996 WHO source, show a likely alteration of the global distribution of dengue due to climate change, with 2.5 billion at risk in the tropics and sub tropics.

Solution to Problem: (A) Because Climate is Predictable

Climate - average over season or longer

as opposed to Weather - day by day. No

predictability of weather beyond 10 days:

Why is climate predictable?

Sea surface temperatureSolar radiationLand vegetationSoil MoistureIce cover

Slow variation over the season:

Observed Precip vs Predicted Precip

0

2

4

6

8

10

12

14

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39Days

mm

Obs Precip

Pred Precip

Avg Obs

Avg Predict

For example:

However there are uncertainties, especially Precipitation

Cannot replicate exactly all processes, e.g., for a given location

Probability statement, e.g., CIMH seasonal prediction:� IRI - ECHAM, CCM3, NCEP � UK - UKMO� Knowledge of Caribbean Climate

Dealing with uncertainty

Solution to Problem: (B) Because of Link

Between Dengue and Climate -

Entomology studies EIP (Type 2): 12 days at 30○ C , 7 days at 32-

35○ C. 5 day decrease in EIP threefold higher

transmission rate of dengue. 3.5○ C rise threefold higher transmission rate

of dengue

One link:

However uncertainties:Uncertain relationshipsSocio-economic factors

3

6

9

30° 33.5°

x

x

x

x

Transmission rate

Temp

For example:

Dealing with uncertainties

RAINFALL TEMPERATURE Heavy Medium Light

High Medium probability

Higher probability

Higher probability

Low Lower probability

Medium probability

Medium probability

Pilot Project: Possible solution to mitigate the impact of climate related dengue Short term

Predict and mitigate climate related impact of dengue over 5 - 10 years

A plan for project is to be produced as part of SIS06 based on results of studies within the project

Execution of pilot project not in SIS06 budget

Plan to be as cost effective as possible taking into account existing agencies.

Workshop to be held for decision makers to market the plan

A learning and capacity building exercise for future adaptation strategies

Policy Makers/Funding Agents

Global ForecastsIRI, NCEP, etc

Climate/Health Directorate

Public Health Officers/Sanitation/etc

Public Health Officials, Media, etc

ClimatePrediction Centre

IM

CSGM

CIMH

Network

Health Surveillance

Outline of structure

Watch/warning

Problems to be encountered

Uncertainty and usefulness of climate forecasts

Deciding how to use the climate forecast to issue a dengue alert

Dissemination of the alert Acceptance of the alert by the population Determining the value of the process.

Questions

What are the methodologies? What are the resource groups providing

information for making the forecasts/alert? How do we measure the skill rate of the

forecast/alert? How can the accuracy of the forecasts and of

linking climate to dengue be improved? What lead times are required?

How do we generate the required forecast/alert?

How and when do we disseminate the alert? How do we educate the vulnerable population and

what can we learn from the population to make the message more effective?

-What are the limitations of the alerts? -What is the value of the alert? -How are the alerts used or applied? -What are the limitations to the use of the alerts? -What are the impediments to the use of the alerts?

To whom are these forecasts valuable? -How valuable? -In what form are the forecasts valuable?

Steps to overcome problems:I) improve prediction

• Advances in the prediction of El Niño, • International centers which make gross predictions

for the Caribbean• Work of researchers in the islands (IM, CSGM,

CIMH) and in the region (CR and Mexico)• 5 to 10 years time: climate prediction in the

Caribbean will become as routine as weather prediction?

Steps to overcome problem: II) Research on linkage

Retrospective studies - determining the characteristics of the epidemiological patterns of dengue fever and its vectors in relation to climate in 21 CAREC Member Countries (CMCs) using past climate and epidemiology data.

Prospective studies of dengue fever / dengue haemorrhagic fever (DHF) in the same 21 CMCs over the first two and half years of this study in relation to changing climate, and of vector abundance using various indicators ( house, container and breteau indices), over the same period and climatic conditions.

Steps to overcome problems: III) showing the way forwardInstitutions such as IRI (climate/social

scientists, psychologists)Publication (‘Under the Weather’)

climate forecasts, epidemiology and environmental fieldwork predictive models

vulnerability assessment, risk analysis Watch/warning response strategy and communication.

Climate

forecasts

Ongoing epidemiological

surveillance and

environmental observations

Disease

watch/warning

Risk analysis,

vulnerability

assessment

Response

strategy

Public

communication

Evaluation,

feedback

Nevertheless we should have faith in science:

•Twenty years ago, we knew very little about predicting climate and El Niño events, much less the connection between Climate Change, El Niño and dengue. What will we know twenty years from now?

“Everybody talks about the weather but nobody does anything about it” Mark Twain (1835-1910)

SIS06: “We can’t change the weather, but we can do something about it”

Have Faith in Science

The End