The Dengue-Climate Problem

2. 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

3. 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.

4. 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.

5. 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.

6. 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:

7. Why is climate predictable? Slow variation over the season: • Sea surface temperature • Solar radiation • Land vegetation • Soil Moisture • Ice cover

8. For example:

9. 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

10. Dealing with uncertainty

11. Solution to Problem: (B) Because of Link Between Dengue and Climate - One link: • 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 • However uncertainties: • Uncertain relationships • Socio-economic factors

12. For example: Transmission rate x 9 6 x x 3 x 33.5° 30° Temp

13. Dealing with uncertainties

14. 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

15. Policy Makers/ Funding Agents Global Forecasts IRI, NCEP, etc Network Climate/Health Directorate Climate Prediction Centre Health Surveillance CSGM Watch/warning IM CIMH Public Health Officials, Media, etc Public Health Officers/Sanitation/etc Outline of structure

16. 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.

17. Questions How do we generate the required forecast/alert? • 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?

18. 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?

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

20. 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?

21. 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.

22. Steps to overcome problems: III) showing the way forward • Institutions 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.

23. Risk analysis, vulnerability assessment Climate forecasts Disease watch/warning Public communication Ongoing epidemiological surveillance and environmental observations Response strategy Evaluation, feedback

24. Have Faith in Science • 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”

25. The End