[Source: Proceedings of the National Academy of Sciences of the United States of America, full page: (LINK). Abstract, edited.]
Global risk model for vector-borne transmission of Zika virus reveals the role of El Niño 2015
Cyril Caminade a,b,1, Joanne Turner a, Soeren Metelmann b,c, Jenny C. Hesson a,d, Marcus S. C. Blagrove a,b, Tom Solomon b,e, Andrew P. Morse b,c, and Matthew Baylis a,b
Author Affiliations: a Department of Epidemiology and Population Health, Institute of Infection and Global Health, University of Liverpool, Liverpool CH64 7TE, United Kingdom; b Health Protection Research Unit in Emerging and Zoonotic Infections, University of Liverpool, Liverpool L69 3GL, United Kingdom; c Department of Geography and Planning, School of Environmental Sciences, University of Liverpool, Liverpool L69 7ZT, United Kingdom; d Department of Medical Biochemistry and Microbiology, Zoonosis Science Center, Uppsala University, Uppsala 751 23, Sweden; e Department of Clinical Infection, Microbiology and Immunology, Institute of Infection and Global Health, University of Liverpool, Liverpool L69 7BE, United Kingdom
Edited by Anthony A. James, University of California, Irvine, CA, and approved November 14, 2016 (received for review September 2, 2016)
This study quantifies the impact of climate variability on Zika virus (ZIKV) transmission by two mosquito vectors with distinct characteristics: Aedes aegypti and Aedes albopictus. Observed climate data were used to dynamically drive a two vectors–one host R0 epidemiological model. Our modeling results indicate that temperature conditions related to the 2015 El Niño climate phenomenon were exceptionally conducive for mosquito-borne transmission of ZIKV over South America. The virus is believed to have entered the continent earlier in 2013. This finding implicates that such a large ZIKV outbreak occurred not solely because of the introduction of ZIKV in a naive population, but because the climatic conditions were optimal for mosquito-borne transmission of ZIKV over South America in 2015.
Zika, a mosquito-borne viral disease that emerged in South America in 2015, was declared a Public Health Emergency of International Concern by the WHO in February of 2016. We developed a climate-driven R0 mathematical model for the transmission risk of Zika virus (ZIKV) that explicitly includes two key mosquito vector species: Aedes aegypti and Aedes albopictus. The model was parameterized and calibrated using the most up to date information from the available literature. It was then driven by observed gridded temperature and rainfall datasets for the period 1950–2015. We find that the transmission risk in South America in 2015 was the highest since 1950. This maximum is related to favoring temperature conditions that caused the simulated biting rates to be largest and mosquito mortality rates and extrinsic incubation periods to be smallest in 2015. This event followed the suspected introduction of ZIKV in Brazil in 2013. The ZIKV outbreak in Latin America has very likely been fueled by the 2015–2016 El Niño climate phenomenon affecting the region. The highest transmission risk globally is in South America and tropical countries where Ae. aegypti is abundant. Transmission risk is strongly seasonal in temperate regions where Ae. albopictus is present, with significant risk of ZIKV transmission in the southeastern states of the United States, in southern China, and to a lesser extent, over southern Europe during the boreal summer season.
Zika virus – R0 – model – El Niño – Ae. aegypti – Ae. albopictus
1 To whom correspondence should be addressed. Email: Cyril.Caminade@liverpool.ac.uk.
Author contributions: C.C., T.S., A.P.M., and M.B. designed research; C.C., J.T., and S.M. performed research; J.T. developed the analytical framework of the model; C.C., J.T., S.M., and M.S.C.B. analyzed data; J.C.H. conducted the large literature review; and C.C. and M.B. wrote the paper with input from all coauthors.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
Data deposition: Model output is publicly available on the Open Science framework platform at osf.io/ubwya/.
This article contains supporting information online at http://www.pnas.org/lookup/suppl/doi:10.1073/pnas.1614303114/-/DCSupplemental.
Freely available online through the PNAS open access option.
Keywords: Zika Virus; El Nino.