Japanese Encephalitis as an Emerging Virus: The Emergence and Spread of Japanese Encephalitis Virus in Australasia J.S. MACKENZIE, C.A. JOHANSEN, S.A. RITCHIE, A.F. VAN DEN HURK, and R.A. HALL Introduction .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 49 2 Background. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 51 2.1 JE and Other Flaviviruses ofindonesia . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 51 2.1.1 The Western Indonesian Archipelago (Sumatra, Java, Kalimantan, Bali) . . . . . . . . . .. 51 2.1.2 The Eastern Indonesian Archipelago (Wallacea) . . . . . . . . . . . . . . . . . . . . . . . .. 52 2.2 JE and Other Flaviviruses of Australasia . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 53 2.2.1 Flaviviruses of Papua New Guinea and Irian Jaya . . . . . . . . . . . . . . . . . . . . . . .. 53 2.2.2 Flaviviruses of Australia. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 54 3 The Emergence of JE in Australasia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 55 3.1 The Emergence of JE Virus in the Torres Strait of Northern Australia . . . . . . . . . . .. 55 3.2 JE Virus in Papua New Guinea and Irian Jaya. . . . . . . . . . . . . . . . . . . . . . . . .. 58 4 Vectors and Vertebrate Hosts: The Potential for Establishment in Australasia . . . . . . .. 59 4.1 Entomological Studies: JE Vectors in Australasia. . . . . . . . . . . . . . . . . . . . . . . .. 60 4.2 Vertebrate Hosts of JE and JE Serogroup Viruses in Australasia. . . . . . . . . . . . . . .. 61 5 Possible Mechanisms of Spread of JE into and within Australasia . . . . . . . . . . . . . .. 64 6 The Potential of JE to Spread into the Pacific . . . . . . . . . . . . . . . . . . . . . . . . .. 67 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 67 1 Introduction Japanese encephalitis (JE) virus has a great propensity to spread, expanding its range through much of southeastern Asia in the past four decades (UMENAI et al. 1985; BURKE and LEAKE 1988; VAUGHN and HOKE 1992; MONATH and HEINZ 1996). In the 1990s, JE spread into southern Pakistan (IGARASHI et al. 1994) and to Haryana State (PRASAD et al. 1993) and Kerala State (DHANDA et al. 1997) in northwestern and southwestern India, respectively. In the east, JE has invaded the eastern Indonesian archipelago, New Guinea, and the Torres Strait of northern Australia (HANNA et al. 1996b; MACKENZIE et al. 1997a). The eastward spread of Department of Microbiology and Parasitology, The University of Queensland, Brisbane, Queensland 4072, Australia Tropical Public Health Unit. Queensland Health, PO Box I \03, Cairns, Queensland 4870, Australia J. S. Mackenzie et al. (eds.), Japanese Encephalitis and West Nile Viruses © Springer-Verlag Berlin Heidelberg 2002