El Niño Southern Oscillation, overseas arrivals and imported chikungunya cases in Australia: A time series analysis

Xiaodong Huang; Wenbiao Hu; Laith Yakob; Gregor J Devine; Elizabeth A McGraw; Cassie C Jansen; Helen M Faddy; Francesca D Frentiu

doi:10.1371/journal.pntd.0007376

El Niño Southern Oscillation, overseas arrivals and imported chikungunya cases in Australia: A time series analysis

PLoS Negl Trop Dis. 2019 May 20;13(5):e0007376. doi: 10.1371/journal.pntd.0007376. eCollection 2019 May.

Authors

Xiaodong Huang¹, Wenbiao Hu², Laith Yakob³, Gregor J Devine⁴, Elizabeth A McGraw⁵, Cassie C Jansen⁶, Helen M Faddy⁷, Francesca D Frentiu¹

Affiliations

¹ School of Biomedical Sciences, Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Queensland, Australia.
² School of Public Health and Social Work, Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Queensland, Australia.
³ Department of Disease Control, London School of Hygiene and Tropical Medicine, London, United Kingdom.
⁴ Mosquito Control Laboratory, QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia.
⁵ College of Agricultural Sciences, Pennsylvania State University, Pennsylvania, United States of America.
⁶ Communicable Diseases Branch, Department of Health, Queensland Health, Herston, Queensland, Australia.
⁷ Research and Development, Australian Red Cross Blood Service, Brisbane, Queensland, Australia.

Abstract

Background: Chikungunya virus (CHIKV) is an emerging mosquito-borne pathogen circulating in tropical and sub-tropical regions. Although autochthonous transmission has not been reported in Australia, there is a potential risk of local CHIKV outbreaks due to the presence of suitable vectors, global trade, frequent international travel and human adaptation to changes in climate.

Methodology/principal findings: A time series seasonal decomposition method was used to investigate the seasonality and trend of monthly imported CHIKV cases. This pattern was compared with the seasonality and trend of monthly overseas arrivals. A wavelet coherence analysis was applied to examine the transient relationships between monthly imported CHIKV cases and southern oscillation index (SOI) in time-frequency space. We found that the number and geographical distribution of countries of acquisition for CHIKV in travellers to Australia has increased in recent years. The number of monthly imported CHIKV cases displayed an unstable increased trend compared with a stable linear increased trend in monthly overseas arrivals. Both imported CHIKV cases and overseas arrivals showed substantial seasonality, with the strongest seasonal effects in each January, followed by each October and July. The wavelet coherence analysis identified four significant transient relationships between monthly imported CHIKV cases and 6-month lagged moving average SOI, in the years 2009-2010, 2012, 2014 and 2015-2016.

Conclusion/significance: High seasonal peaks of imported CHIKV cases were consistent with the high seasonal peaks of overseas arrivals into Australia. Our analysis also indicates that El Niño Southern Oscillation (ENSO) variation may impact CHIKV epidemics in endemic regions, in turn influencing the pattern of imported cases.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Australia / epidemiology
Chikungunya Fever / epidemiology*
El Nino-Southern Oscillation*
Humans
Seasons
Spatio-Temporal Analysis
Travel

Grants and funding

This research was funded by the Australian National Health and Medical Research Council (APP1125317). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.