A dengue vector-control program was conducted on Koh Samui, an island in the Gulf of Thailand, in 1968. Virus-isolation data gathered in support of this program indicated that a single dengue serotype, dengue-4, was active at the time; 63 dengue isolates from mosquitoes and 2 from patients were identified as type 4, the same serotype that prevailed on the island in 1967. Variability was noted in neutralization of many strains by a single lot of type-specific immune serum, as had been observed in previous studies of low-passage tissue-culture strains of dengue virus. Dengue viruses were isolated from both Aedes aegypti and Aedes albopictus, the former having the higher infection rate. All dengue isolates were made from in or around homes of patients with laboratory evidence of dengue infection. The sensitivity of the LLC-MK2 delayed-plaque system was emphasized in these studies since only 66.7% of isolates were recovered with the standard plaque assay.
Deceased. Please direct reprint requests to Dr. Winter.
Present address: Preventive Medicine Division, Office of The Surgeon General, Washington, D. C. 20314.
U.S. mailing address: SEATO Medical Project, U.S. Component, APO San Francisco, California 96346.