Presentation on theme: "Dengue proposal Considerations for design of the phase II follow up."— Presentation transcript:
Dengue proposal Considerations for design of the phase II follow up
Background DPSEEA was used to introduce the notion of urban ecosystem health. The framework was applied to chronic aspect of urban conditions in Cayo Hueso. Participatory approaches were used to define key indicators. The findings: »Measurable improvements in subjective indicators. »Inconclusive change in more objective indicators.
Follow on research for dengue Reapply the phase I methods again. Elaborate on DPSEEA introducing: »the importance of context, »ecosystem processes and their interactions »Broader ecosystem health/integrity perspective. Refine the indicators: »learning why there is a gap between the subjective and objective outcomes. Create a new decision-making and evaluation framework emphasizing learning objectives and adaptive management: »Dengue is an episodic risk in Cuba. Monitoring and intervention for such problems are not the same as those of a chronic issue such as housing.
Lessons from Phase I Relative importance of exogenous factors. Challenges in attributing effects to intervention without a control population. …
Opportunity in Phase II Design FeatureRetrospective study Prospective study Indicatorsyes Monitoring strategynoyes Intervention strategynoyes Learning & Adaptive management noyes
Why does an overall framework matter? Monitoring is like our eyes Decision-making is like our brain We cannot look everywhere We cannot think of everything We need to think about costs and benefits of every monitoring and intervention action. We need to find the efficient and effective set of observations (monitoring) that allow appropriate actions (campaigns).
Issues in control of epidemics Monitoring is less than perfect »e.g. infected are asymptomatic but have viremia »Symptoms of potential infection may go mal-reported (know 5 day bed-rest could lead to over reporting (if compensated) and under reported (if time substitution is unavailable to the patient). Intervention efficacy is less than perfect: »depends on social acceptance, »depends on suitability to ecosystem (e.g. closed buildings), »depends on being timely, which is itself reliant on frequency of monitoring and speed of interpretation. Direct and intended benefits of monitoring depend on the efficacy of interventions that could be triggered by it. Imperfect monitoring and interventions erodes social acceptance and trust.
Three dimensions to evaluation Effects: »direct and intended »indirect and ancillary Benefits and costs: »cases of dengue and DHF »other health effects »improved living conditions, … Measures: »Objective, subjective »Information flow and feedback to decision making The challenge of sustainability in the absence of a signal The opportunity for sustainability through indirect benefits
An Ideal Policy Has community support. Has positive impacts. Is monitored and enforced effectively. Has self-righting properties. Has free-drivers. Meets more than one objective.
Take the case of dengue in Cuba: We need to identify the policy goal, approach & constraints Goal »prevent dengue Actions: »Reduce breeding sites for A. aegypti »Eradicate mosquito population »Isolate potential infected people from healthy Means: »Monitoring, interpretation and dissemination of information, »Decision-making processes Constraints: »The time of field workers »The time of households »The cost of fumigation (money and incidental health impacts) »The implications of forced bed-rest for feverish people »Loss of public interest for participation
The overall framework Ecology The scientific input Society Goals and values What outcome to encourage and when How GovernanceMonitoring Intervention The ecologically possible The socially preferred
Design alternatives monitor what? monitor how? when to act? what to do? Find best system 1. Mosquito habitat 2. Mosquito density 3. Disease locally 4. Disease regionally 5. Weakly active network until trigger 6. Adaptive hotspot monitoring a)Destroy habitat b)Destroy mosquito c)Change behaviour d)… [1 » a] [2 » a+b] [3 » a+b+c] [2+3 » a+b+b] [4 » 1 » a+b] …
How should the monitoring/intervention evolve at different levels of force of infection? The iterative cycles of monitoring and intervention. E.g.: The first 90% can be controlled through identification and elimination of the 1st levels risk factors. The next 90% through identification of 2nd level risk factors and interventions The next 90% through identification of 3rd level risk factors and interventions. The next 90% … The rule for when to stop is determined by the whole human-vector-virus ecology. For a disease that is hard to transmit, we can stop at the level of the first risk factors. For a disease that is easily transmitted we need to go to understanding and controlling smaller and smaller risk factors.
Illness Transmission of Dengue Virus by Aedes aegypti Days 0581216202428 Human #1Human #2 Viremia Mosquito feeds & acquires virus Mosquito refeeds & transmits virus A.aegypti in ecosystem Infected human in ecosystem Extrinsic incubation period (~9 days) Intrinsic incubation period (~7 days)
Transmission of Dengue Virus by Aedes aegypti Viremia Days 0581216202428 Human #1Human #2 Illness Mosquito feeds & acquires virus Mosquito refeeds & transmits virus Viremia Illness A.aegypti in ecosystem Infected human in ecosystem Fumigation kills mosquitoes
Transmission of Dengue Virus by Aedes aegypti Viremia Days 0581216202428 Human #1Human #2 Illness Mosquito feeds & acquires virus Mosquito refeeds & transmits virus Viremia Illness A.aegypti in ecosystem Infected human in ecosystem Breeding site elimination
Transmission of Dengue Virus by Aedes aegypti Viremia Days 0581216202428 Human #1Human #2 Illness Mosquito feeds & acquires virus Mosquito refeeds & transmits virus Viremia Illness Forced bedrest isolates viremia from vector A.aegypti in ecosystem Infected human in ecosystem
Research Ideas from UBC partners Retrospective: A full evaluation (costs and benefits, intended and unintended) of the monitoring-intervention program. »What can be learned about dengue ecology because of the extra- ordinary setting? »A retrospective of health and environmental impacts of the control campaign in 2002. Prospective: How should the monitoring/intervention evolve at different risks of epidemic? (refinement of methodology given Cubas special situation) What are the pre-requisites for introducing self reinforcing and self-adjusting elements to the process?
Outcomes, Indicators & Interventions (to be evaluated) Indicator > critical value Breeding site control LarvicideFumigationBed rest for the feverish Reliable water & sewage Costs / Benefits Spatial- temporal coverage Breeding sites -- Ex ante risk identification Every 15 days erery place Mosquito population -Ex post risk estimation Every week Serology - -Costly? Slow?Travellers, Feverish Community participation Builds community needs to pay off! Only for acts with visible benefits Deployment cost / benefit Dengue, water quality, … Risk to ecosystem Free riders, non-reporters HUGE benefit Definite NEED Deployment frequency Every 15 days Flow relatedEvery 15 days5 days10 years
C&B of Interventions: monitoring blood samples Costs High cost May be too late for prevention epidemic Loss of privacy Benefits Screening for other diseases & behavioural change Weakness Could change behaviour in seeking medical help Strength Least ambiguous test of dengue Prerequisite to level of concern about DHF
C&B of Interventions: destruction of habitat Costs Continuous effort High labour input Benefits Cleaner environment Weakness Some households will not be able to comply. As the vector is not eradicated but pressed for habitat it will change its behaviour Strength Could contribute to community spirit if organized as a social event.
C&B of Interventions: quarantine Costs Loss of work Familiar discord More babies? Benefits More babies? Good to have a rest Weakness Hosts have viremia long before they show symptoms. Non-compliance Could change behaviour in seeking medical help Strength It may provide spatially specific information for concentration of effort.
C&B of Interventions: fumigation & spraying Costs Needs coordination of episodic effort & opportunity cost of labour and material input Contamination of environment Loss of ecosystem integrity Human health effects Benefits Destruction of mosquitoes Weakness Closed houses. Impatient home owners. Poor public relations. Does not kill larvae Strength Fast deployment Politically visible Triggers behavioural change
C&B of Interventions: reliable domestic water supply Costs High investment costs Only part of the solution Benefits Eliminates major habitats at home Reduced water-borne epidemics Better hygiene Saves time Reduces injury Weakness A long lead time Strength Strong public support Will be easier to maintain
What aspects of the ecosystem-health approach are more readily adopted, why? Does the approach have value if partially adopted? »Spatial and functional organization challenges? »What critical aspects are missing and why? Does possibility of formal risk assessment, cost and benefit estimation, … approaches impact adoption patterns? »They did not resonate to the notion of cost. »How is value of information get translated into something of similar implication here? What would be the features of a self-righting approach?
Need to identify goal, approach & constraints Goal »prevent dengue Actions: »Reduce breeding sites for A. aegypti »Eradicate mosquito population »Isolate potential infected people from healthy Means: »Monitoring, interpretation and dissemination of information, »Decision-making processes Constraints: »The time of field workers »The time of households »The cost of fumigation (money and incidental health impacts) »The implications of forced bed-rest for feverish people »Loss of public interest for participation