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

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.

Estimating underobservation and the full size of the 2016 Zika epidemic in Rio de Janeiro

“…Although estimating R 0 was not the main focus of this study, the values obtained (2.53% (95% CI: 1.59−3.45%)) are consistent with previous estimates [8,16,17].…”

“…With this knowledge, we assumed that the percentage of fertility reduction caused by Zika (mz) follows a beta distribution whose parameters α mz , and β mz imply a mean of 0.5 and 95% probability between 0.25 and 0.75. The distribution of mz is given by Eq (17).…”

Arbovirus Vectors of Epidemiological Concern in the Americas: A Scoping Review of Entomological Studies on Zika, Dengue and Chikungunya Virus Vectors

“…Five studies modelled transmission dynamics for Zika virus [138,180–183]. Lourenço et al [138] used vectorial capacity as a means of prediction, Marini et al [180] and Majumder et al [185] used vector abundance and human case data, and Villela et al [182] and Ospina et al [183] used disease notification and natural history.…”

A conceptual model for optimizing vaccine coverage to reduce vector-borne infections in the presence of antibody-dependent enhancement

“…Past studies have estimated the Zika basic reproduction number to be 2.33 (95% CI 2.15-2.51) in French Polynesia [39], 2.33 (95% CI 1.97-2.97) in Rio de Janeiro, Brazil [40], and 2.1 in Mexico [41]. The dengue basic reproduction number has also been estimated to be 2.93 (95% CI 1.89-5.47) in French Polynesia [42], 2.32 (95% 2.07-2.60) in Brazil [42], and 3.09 (95% CI 2.34-3.84) in Mexico [43].…”