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. 2013 Jul 16;8(7):e68137.
doi: 10.1371/journal.pone.0068137. Print 2013.

An explosive epidemic of DENV-3 in Cairns, Australia

Affiliations

An explosive epidemic of DENV-3 in Cairns, Australia

Scott A Ritchie et al. PLoS One. .

Erratum in

  • PLoS One. 2013;8(12). doi:10.1371/annotation/a8dfd4ee-f4b7-443e-bf78-ebb0dab4e55b
  • PLoS One. 2014;9(8):e105846

Abstract

From November 2008-May 2009 Cairns Queensland Australia was struck by an explosive epidemic of DENV-3 that exceeded the capacity of highly skilled dengue control team to control it. We describe the environmental, virological and entomological factors associated with this outbreak to better understand the circumstances leading to its occurrence. Patient interviews, serological results and viral sequencing strongly suggest that the imported index case was infected in Kalimantan, Indonesia. A delay in notification of 27 days from importation of the index case until Queensland Health was notified of dengue transmission allowed the virus to amplify and spread unchecked through November 2008. Unseasonably warm weather, with daily mean temperatures exceeding 30 °C, occurred in late November and would have shortened the extrinsic incubation period of the virus and enhanced transmission. Analysis of case movements early in the outbreak indicated that the total incubation period was as low as 9-11 days. This was supported by laboratory vector competence studies that found transmission by Aedes aegypti occurred within 5 days post exposure at 28 °C. Effective vector competence rates calculated from these transmission studies indicate that early transmission contributed to the explosive dengue transmission observed in this outbreak. Collections from BG sentinel traps and double sticky ovitraps showed that large populations of the vector Ae. aegypti occurred in the transmission areas from November - December 2008. Finally, the seasonal movement of people around the Christmas holiday season enhanced the spread of DENV-3. These results suggest that a strain of DENV-3 with an unusually rapid transmission cycle was able to outpace vector control efforts, especially those reliant upon delayed action control such as lethal ovitraps.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Aedes aegypti populations during the epidemic.
Collection of female Aedes aegypti in sticky ovitraps (n = 64) and Biogents sentinel traps (BGS, n = 14) set in Cairns, Australia. Low SO collections from May-Nov. 2008 reflect poor capture by a dry glue temporally used in the trap.
Figure 2
Figure 2. Epidemic curve of the DENV-3 outbreak.
Number of confirmed cases of DENV-3 in Cairns region by week, and number of suburbs with active weekly transmission.
Figure 3
Figure 3. Phylogeny of DENV-3 from Cairns, Australia.
Maximum likelihood (ML) phylogeny of DENV-3 from Cairns, Australia, from 1998 and 2008 (in bold, with asterix), based on whole-genome sequences. Several other isolates from the region were also sequenced and included (shown in bold, GenBank Accession numbers JN575563-80), along with publicly available sequences (accession numbers available upon request). Analysis was implemented in RAxML Black Box webserver under the GTR+I+G model of evolution, including support at nodes based on 100 ML replicates. Sample labeling includes serotype/ISO country code/strain/year of collection. Genotypes I through V are indicated on the far right.
Figure 4
Figure 4. Effective vector competence of the Cairns DENV-3.
Top: The change in vector competence over time through a population of vectors is a dynamic process. Here the difference in dynamic vector competence between the 2008/09 (dashed line) and 1997/98 (solid line) strains is shown. These linear functions then replace the static measure of vector competence and are used to calculate the effective vector competence (EVC). Bottom: EVC curves for the two strains- 2008/09 (foreground, solid) and 1997/98 (background, checkered)- are shown. These curves utilize the dynamic vector competence function over time and also weight each day’s value for the effect of mosquito mortality.
Figure 5
Figure 5. Proposed transmission cycle of the Cairns DENV-3.
Schematic of transmission cycle (A) and intervention results (B) for typical dengue (EIP = 10 days) and quick dengue (C; EIP = 5 days).

References

    1. Bhatt S, Gething PW, Brady OJ, Messina JP, Farlow AW, et al. The global distribution and burden of dengue. Nature doi: 10.1038/nature12060. [Epub ahead of print]. - DOI - PMC - PubMed
    1. Ritchie SA, Hanna JN, Hills SL, Piispanen JP, McBride WJH, et al. (2002) Dengue control in north Queensland, Australia: case recognition and selective indoor residual spraying. Dengue Bulletin 26: 7–13.
    1. Perich MJ, Rocha NO, Castro AL, Alfaro AW, Platt KB, et al. (2003) Evaluation of the efficacy of lambda-cyhalothrin applied by three spray application methods for emergency control of Aedes aegypti in Costa Rica. J Am Mosq Control Assoc 19: 58–62. - PubMed
    1. Gubler DJ (1989) Aedes aegypti and Aedes aegypti-borne disease control in the 1990s: top down or bottom up. Charles Franklin Craig Lecture. Am J Trop Med Hyg 40: 571–578. - PubMed
    1. Vazquez-Prokopec GM, Chaves LF, Ritchie SA, Davis J, Kitron U (2010) Unforeseen costs of cutting mosquito surveillance budgets. PLoS Negl Trop Dis 4: e858. - PMC - PubMed

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