Emergence of a new lineage of dengue virus type 2 identified in travelers entering Western Australia from Indonesia, 2010-2012

Abstract

Dengue virus (DENV) transmission is ubiquitous throughout the tropics. More than 70% of the current global dengue disease burden is borne by people who live in the Asia-Pacific region. We sequenced the E gene of DENV isolated from travellers entering Western Australia between 2010-2012, most of whom visited Indonesia, and identified a diverse array of DENV1-4, including multiple co-circulating viral lineages. Most viruses were closely related to lineages known to have circulated in Indonesia for some time, indicating that this geographic region serves as a major hub for dengue genetic diversity. Most notably, we identified a new lineage of DENV-2 (Cosmopolitan genotype) that emerged in Bali in 2011-2012. The spread of this lineage should clearly be monitored. Surveillance of symptomatic returned travellers provides important and timely information on circulating DENV serotypes and genotypes, and can reveal the herald wave of dengue and other emerging infectious diseases.

Figure 1. Origin and diversity of dengue viruses isolated from travelers entering Western Australia during 2010–2012.

(A) Geographic origins of all imported DENV; (B) Geographic origin of individual DENV serotypes.

Figure 2. Phylogenetic tree of 2289 DENV-1 E sequences including 28 from travelers to Australia.

Because of the very large numbers of sequences involved, where possible phylogenetic clusters have been ‘collapsed’ (such they are they depicted as triangles) to reveal the positions of the Australian viruses in more detail. Major genotypes and geographic locations of sequences are indicated. Those viruses sampled from travellers to Australia are colored red, numbered according to phylogenetic lineage (Table 1), with the likely place of infection noted. Bootstrap support values (>70%) are shown for key nodes and all horizontal branch lengths are drawn to a scale of nucleotide substitutions per site. The tree is mid-point rooted for clarity only.

Figure 3. Phylogenetic tree of 2263 DENV-2 E sequences including 46 from travellers to Australia.

Other features are as they are described in Fig. 2.

Figure 4. Phylogenetic tree of 1256 DENV-3 E sequences including three from travellers to Australia.

Other features are as they are described in Fig. 2.

Figure 5. Phylogenetic tree of 670 DENV-4 E sequences including nine from travellers to Australia.

Other features are as they are described in Fig. 2.