Dengue Control on an Island in the Gulf of Thailand

III. Effect on Transmission of Dengue Virus to Man

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  • Medical Research Laboratory, SEATO Medical Project, Rajavithi Road, Bangkok, Thailand

An Aedes aegypti control program on the island of Koh Samui, Thiland, was evaluated in terms of human infection, both clinical and subclinical. Seroconversion rates to dengue were examined monthly in a sample of school children. Crude antibody conversion rates were about 3 per 100 per month before the control program. Because of small sample size, conversion rates after control could not be accurately determined; by this measurement, transmission was not completely interrupted. Clinical cases were classified by clinical course and serological response. A total of 27 dengue and probable dengue cases were seen. Among these were two of dengue shock syndrome and six of hemorrhagic fever. No case had a primary-type antibody response. Disease patterns were similar to those seen in previous years, except that only one case was recorded after the control program. The control program apparently resulted in marked decreases in vector population, in vector infection rates, and in human disease.

Author Notes

Present address: Preventive Medicine Division, Office of the Surgeon General, Washington, D. C. 20314.

Present address: Suvit Clinic, Ang Thong, Koh Samui, Surat Thani, Thailand.

Present address: Arbovirus Research Laboratory, Department of Bacteriology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia.

Present address: Department of Virus Diseases, Walter Reed Army Institute of Research, Walter Reed Army Medical Center, Washington, D. C. 20012.

U. S. mailing address: SEATO Medical Project, U. S. Component, APO San Francisco, California 96346.