Fogging activities are carried out as soon as a suspected case of dengue is notified to the health authority. For a single case of dengue, perifocal fogging 200m around the patient's house using the portable thermal fogging is carried out. For outbreak situation, ULV fogging is used to cover the whole locality. During dengue outbreak, the first adulticidal treatment is normally followed by a second application 7-10 days later. The two treatment cycle is based on the life-cycle of the Aedes mosquitoes and the incubation period of the virus in the mosquito. The outbreak is declared as over once it has been possible to achieve a 20 day transmission-free period. The insecticide of choice for fogging is malathion in fuel oil for thermal fogging and 96% malathion technical garde for ULV. Air-borne bioassay tests are conducted regularly and to date, there is no indication of resistance developing to the insecticide by the Aedes mosquitoes.
A-numberof problems are encountered in fogging activities, including the following:
1. Some houseowners tend to close the doors and windows during fogging which will reduce the effectiveness of the spray droplets reaching the target mosquitoes.
2. The difficulty of achieving total coverage of all houses and in carrying out second fogging within 7-10 days duration after the first round.
3. The use of newsynthetic pyrethroid insecticides for fogging which are not effective in controlling outbreaks.
4. Private pest control operators conducting fogging without adequate supervision.
HEALTH EDUCATION ACTIVITIESHealth education is an ongoing activity and is continuously strengthened in order to gain public support and cooperation. These activities include health talks, individual advice, demonstrations, distribution of pamphlets, etc. They are carried out during the Aedes surveys from house to house, during fogging operations and case investigations. This activity is intensified during the anti-dengue campaign months of January, April, July and October, especially in dengue-prone or sensitive areas. Demonstrations in the use of larvicides and destruction of breeding places are carried out in the premises inspected. During outbreaks, health education activities are further intensified through the use of mass media (including electronic and print) at various levels. Government agencies, local authorities, and voluntary organizations participate in source reduction activities, 307 printing of education posters and pamphlets and distribution of health education materials. In addition, special health education teams are formed to ensure quicker and fuller coverage of the affected population.
