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Comparative Study
. 2017 Jun;145(8):1649-1657.
doi: 10.1017/S0950268817000358. Epub 2017 Feb 27.

Zika in Rio de Janeiro: Assessment of basic reproduction number and comparison with dengue outbreaks

D A M Villela  1 , L S Bastos  1 , L M DE Carvalho  1 , O G Cruz  1 , M F C Gomes  1 , B Durovni  2 , M C Lemos  2 , V Saraceni  2 , F C Coelho  3 , C T Codeço  1
Affiliations
Comparative Study

Zika in Rio de Janeiro: Assessment of basic reproduction number and comparison with dengue outbreaks

D A M Villela et al. Epidemiol Infect. 2017 Jun.

Abstract

Zika virus infection was declared a public health emergency of international concern in February 2016 in response to the outbreak in Brazil and its suspected link with congenital anomalies. In this study, we use notification data and disease natural history parameters to estimate the basic reproduction number (R 0) of Zika in Rio de Janeiro, Brazil. We also obtain estimates of R 0 of dengue from time series of dengue cases in the outbreaks registered in 2002 and 2012 in the city, when DENV-3 and DENV-4 serotypes, respectively, had just emerged. Our estimates of the basic reproduction number for Zika in Rio de Janeiro based on surveillance notifications (R 0 = 2·33, 95% CI: 1·97-2·97) were higher than those obtained for dengue in the city (year 2002: R 0 = 1·70 [1·50-2·02]; year 2012: R 0 = 1·25 [1·18-1·36]). Given the role of Aedes aegypti as vector of both the Zika and dengue viruses, we also derive R 0 of Zika as a function of both dengue reproduction number and entomological and epidemiological parameters for dengue and Zika. Using the dengue outbreaks from previous years allowed us to estimate the potential R 0 of Zika. Our estimates were closely in agreement with our first Zika's R 0 estimation from notification data. Hence, these results validate deriving the potential risk of Zika transmission in areas with recurring dengue outbreaks. Whether transmission routes other than vector-based can sustain a Zika epidemic still deserves attention, but our results suggest that the Zika outbreak in Rio de Janeiro emerged due to population susceptibility and ubiquitous presence of Ae. aegypti.

Keywords: Basic reproduction number; Zika; dengue.

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Conflict of interest statement

The authors declare no competing financial interests.

Figures

Fig. 1.
Fig. 1.
Epidemic curve of Zika in Rio de Janeiro, 2015–2016 (blue bars). Red dashed line shows the exponential growth of Zika cases, with an estimated constant rate formula image, during the first 7 weeks.
Fig. 2.
Fig. 2.
Estimates of the basic reproduction number for Zika by health districts in Rio de Janeiro.
See this image and copyright information in PMC

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