Molecular epidemiology of dengue 3 viruses and genetic relatedness among dengue 3 strains isolated from patients with mild or severe form of dengue fever in French Polynesia

1 Institut Territorial de Recherches Médicales Louis Malardé, P.O. Box 30 Papeete, Tahiti, French Polynesia 2 Institut Pasteur de Paris, 28 rue du Dr Roux, 75724 Paris Cedex 15, France and 3 Institut Pasteur de Nouméa, B.P. 61 Nouméa, Nouvelle-Calédonie The nucleotide sequences of a short fragment of the envelope protein gene encoding amino acids 25 to 89 of 27 dengue 3 viruses were determined by direct sequencing of PCR-amplified products, and the viruses were compared regarding their time of isolation and geographic distribution. Four distinct genotypic groups were discerned at 6% divergence between nucleotide sequences. The first group contained is olates from the South Pacific (1988 to 1992), Singapore (1973) and Indonesia (1973 to 1991). The second group comprised viruses from Asia (1956 to 1989) including the reference strain H-87. The third was composed of one isolate from Thailand (1971), and the fourth included the early strains from French Polynesia (1964 to 1969) and from Puerto Rico (1963). Furthermore, the difference between early and recent strains from the South Pacific was as high as 12.3%. This observation suggests that the recent epidemics in the South Pacific were probably the consequence of the spread of a new variant that emerged from New Caledonia. However, relatedness between nucleotide sequence and disease severity, or between strains from epidemics with mild disease (New Caledonia) and strains from epidemics with severe disease (French Polynesia) could not be demonstrated. Received 15 April 1993; accepted 22 July 1993.