Distribution of Dengue Cases by State/Division in Myanmar, 2007
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JOINT PLAN OF ACTION SCALING UP DENGUE PREVENTION AND CONTROL FOR THE CYCLONE NARGIS-AFFECTED POPULATIONS June-September 2008 1. SITUATION ANALYSIS In Myanmar dengue fever (DF)/dengue haemorrhagic fever (DHF) is one of the leading causes of morbidity and mortality among children under the age of 10 years, with approximately 85% of cases occurring in this age group. Some adult cases have been reported, especially from rural areas. An annual average of 7,000-10,000 cases of DF/DHF are reported nationwide. However, in recent epidemic years (2001, 2002 and 2007), the number has risen to over 15,000 cases. National figures indicate that the largest number of cases are from Yangon Division. In 2007, Yangon (31%), Ayeyarwaddy Division (16%) and Mon State (15%) accounted for 62% of all reported cases. Reliable forecasting of epidemics is not possible. Distribution of Dengue Cases by State/Division in Myanmar, 2007 Number of dengue cases 2007 0 1- 100 101 - 500 501 - 1,000 1,001 - 2,000 > 2,000 1 Most cases of DF/DHF occur between May and October, during the rainy season, with a peak in July. Monthly distribution of Dengue Cases in Myanmar 2007 and 5-year average (2003 - 2007) 5000 4500 4000 3500 3000 2500 2000 1500 1000 Num ber of Dengue Cases 500 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Months 2007 5-year average The DHF case fatality rate (CFR) varies from 0.2% to 6.25% but is consistently lower in Yangon than in other Divisions and States. The reasons for these differences are unclear, but high to moderate CFRs could be due to (a) admission of a high proportion of DHF/dengue shock syndrome (DSS) cases compared to DF; (2) lack of experienced doctors and nurses; and (c) inadequate equipment for essential clinical laboratory tests, e.g. PCV, platelet counts, WBC. Nevertheless, early detection and effective clinical management are critical for keeping CFRs low. The main mosquito vector of dengue in the country is Aedes aegypti , a highly domesticated species that is found mainly in urban / peri-urban areas in all townships in Yangon and throughout most of the country. In breeds almost exclusively in man-made water-filled receptacles. Aedes albopictus , is also widespread in Myanmar, particularly in more rural settings and may have a secondary role in transmission. Breeding sites are found indoors as well as outdoors. The profile of container habits supporting larval populations of the vector vary between localities. However, in a recent study by Department of Medical Research (Lower Myanmar) supported by TDR on the larval ecology of Aedes aegypti in a sample of Yangon townships, 65% of all adult mosquito production derived from only 4 container habitats: 22% of adult mosquitoes originated from water storage drums, a further 22% from spirit worship flower bowls, 12% from spirit house flower vases and 7% from concrete water storage tanks. The risk of dengue transmission in the cyclone affected areas may be increased among people living in temporary shelters and/or overcrowded conditions, particularly where fresh water is stored in unprotected water containers and rainfall collects in other artificial containers, allowing mosquitoes vectors to proliferate. Damaged and un-repaired roofs in urban areas may also contribute to increased vector populations wherever water accumulates indoors on flooded floors or in basements. Similarly, rainwater collecting in the hollowed-out cavities of felled trees will provide additional new breeding sites. Moreover, rural populations displaced from rural to urban areas are likely to have lower herd immunity to dengue viruses and may therefore facilitate virus transmission in urban areas. 2 As of 10 June 2008, 781 cases of dengue / DHF were reported form Yangon Division, and as of 31 May 2008, 471 case were reported in Ayeyawaddy Division. In the later, over 50% of cases are from rural areas. 2. KEY STRATEGIES 2.1 Disease surveillance National epidemiological surveillance and reporting systems are in place for DF/DHF. Laboratory support for confirmation of DF/DHF is unlikely to be available in some of the severely affected areas. Surveillance is based mainly on the reporting of clinical cases, using WHO case definitions. Additionally, dengue is included in the Early Warning and Reporting System (EWARS) put in place for the cyclone affected areas in Yangon and Ayeyawaddy Divisions. Where available, commercial rapid diagnostic kits for use in the field may also aid outbreak investigation especially in rural areas, but their sensitivity and specificity are limited. 2.2 Clinical management Early recognition and effective clinical management of DHF patients is essential for minimizing case fatality rates and physicians and nurses in areas endemic should be well-trained. Clinical laboratory support for severe cases in referral hospitals is important for monitoring haematocrit and platelet counts and for fluid therapy during critical stages. Hospitals and temporary health facilities should be prepared to respond in the event of outbreaks. 2.3 Vector control Aedes aegypti is the main target of dengue prevention and control measures. It breeds almost entirely in man-made container habitats inside the houses and close to human habitation, particularly items such as rain-filled discarded food and beverage containers, plastic packaging, used tyres, domestic water storage containers, flower vases and any other confined, water-filled containers. 2.3.1 Environmental management Environmental management is the main strategy for reducing dengue vector populations. For all collections of water in receptacles in and around houses and other habitation, the objective is to either eliminate the receptacles or to manage them in ways that do not allow mosquitoes to proliferate. Depending on the type of container and its use, there may be different options, e.g., the collection and removal of discarded items in which rainwater can settle; overturning, crushing or puncturing such items so they do not accumulate water; storing them under shelter. Containers used for storing water at the household should be covered with tight fitting lids to prevent mosquito access or emptied, scrubbed and refilled no less than once per week. Flower vases for spirit houses can be managed in a similar manner to avoid mosquito production. Tree holes can be filled with sand or soil. 2.3.2 Chemical control: insecticides and their application 2.3.2.1 Larvicides Where water is stored in large containers (large tanks, cisterns, etc) which cannot be tightly covered or regularly emptied, insecticides are used to control the larvae. The larvicide temephos, formulated as 1% sand granules, is recommended by WHO for application and it is safe use in drinking water. It has a residual effect and can provide control for 6-8 weeks at the recommended dosage of 1 ppm (10g/100 litres). 3 2.3.2.2 Adulticides Space spraying to kill adult mosquitoes (thermal or cold fogging) is an epidemic contingency measure and should only be carried out in support of other measures that provide longer term control of the mosquitoes in their man-made larval habitats. Where fogging is warranted, e.g., in crowded campsites for displaced persons, or adjacent urban settlements where (a) mosquito biting is occurring during daylight hours (indicating the presence of one or other of the main dengue vectors, Aedes aegypti and Aedes albopictus ) or (b) suspected or probable cases of DF and/or DHF are reported, the entire campsite or settlement will be systematically fogged, preferably in the early morning between dawn and 09:00 hrs, when the adult mosquitoes are active and meteorological conditions are usually most favourable (or if necessary, in the late afternoon between 16:30 hrs and dusk). This allows the insecticide fog to drift slowly through the area. Fogging has only a transient effect, killing flying mosquitoes which come into direct contact with the insecticide droplets. As soon as the insecticide cloud has drifted away the effect is gone. Fogging should not be carried out during periods of rainfall. Machine operating procedures and insecticide label instructions must be followed. The procedure should repeated twice per week for at least two weeks or until no further cases are reported. All machine operators and insecticide handlers must be trained prior to the operations and provided with the necessary protective equipment. Resource documents: Space spray application of insecticides for vector and public health pest control. A practitioner's guide. http://whqlibdoc.who.int/hq/2003/WHO_CDS_WHOPES_GCDPP_2003.5.pdf Safe use of pesticides. In Pesticides and their application for the control of vectors and pests of public health importance. Chapter 2 pp 11-20. http://whqlibdoc.who.int/hq/2006/WHO_CDS_NTD_WHOPES_GCDPP_2006.1_eng.pdf 2.4 Social mobilization Effective control of Aedes aegypti requires a multi-disciplinary approach, with involvement of the at-risk communities in environmental management. Key groups within those communities are mobilized to undertake measures to reduce the number of containers that are producing mosquitoes, e.g., housewives, schoolchildren, monks, shopkeepers. Clear behavioural messages and channels of communication to reach the target groups must be identified. Other resource documents Prevention and control of dengue and dengue haemorrhagic fever. Comprehensive Guidelines (WHO SEARO No. 29) 1999 http://searo.who.int/EN/Section10/Section332/Section554.htm 4 3. OPERATIONAL PLAN 3.1 Objectives o To reduce the risk and/or intensity of transmission during the current transmission season o To suppress or contain localized outbreaks o To minimize DHF case fatality rates o To strengthen national capacity for the prevention and control of DF/DHF 3.2 Target Areas 3.2.1 Yangon townships with highest DF/DHF case reporting rates – 1st priority The first priority is the 11 townships in Yangon Division (Table 1) with highest average annual number of DF/DHF cases (2005-2007).