Projecting the end of the Zika virus epidemic in Latin America: a modelling analysis

Kathleen M O’Reilly; Rachel Lowe; W John Edmunds; Philippe Mayaud; Adam Kucharski; Rosalind M Eggo; Sebastian Funk; Deepit Bhatia; Kamran Khan; Moritz U Kraemar; Annelies Wilder-Smith; Laura C Rodrigues; Patricia Brasil; Eduardo Massad; Thomas Jaenisch; Simon Cauchemez; Oliver J Brady; Laith Yakob

aegypti is a largely urban dwelling mosquito and that arboviral diseases have been observed to be spread by movement of infected humans, 39, 40 this assumption is likely to be valid. However, while we predict the outbreak to largely be over in these large cities, smaller more remote cities and peri-urban areas may still have susceptible individuals and experience cases. Should additional sub-national data on the timing of the peak become available, the model fitting and projections can easily be updated. Case reporting rates indicate a lower rate within countries that report only confirmed cases, and the rates within Brazil, El Salvador, Martinique, Puerto Rico, and Suriname align well with other estimates measured using alternative methods. 21, 41, 42 Despite the short-comings in the available data, we present the most up-to-date and robust predictions of Zika incidence in 2018. As the projected incidence is consistently low across all model runs, this finding is quite robust to the variability accounted for in the model. Validation of these findings are necessary through multi-site population representative seroprevalence surveys across LAC to monitor seroconversion to ZIKV, such as in Netto et al.. 19 Reporting of cases within LAC has reduced markedly since the downgrading of ZIKV from a public health emergency of international concern to an ongoing public health challenge (in November 2018). 43 Consequently, it remains difficult to compare these projections to incidence data for 2018. This research has highlighted that within LAC the spread of ZIKV was better represented by a gravity model than flight movements. This may seem surprising as flight data are cited as a source of emerging infections, such as ZIKV. 44 But cars and public transportation are used for most journeys; and the movement of people impacts the spatial spread of vector-borne diseases. 38, 45 Perhaps for highly transmissible infectious diseases movements facilitated by flights are sufficient for predicting introduction of a pathogen in a new population, but this analysis suggests that triggering of a ZIKV outbreak may require more frequent exposure than air travel. The migration patterns assumed within each model are quite different in LAC (see Supporting Information), suggesting that models which have not tested the relative fit of each and use one alone could be prone to errors in estimated spread of ZIKV. In comparison to mobility modelling in North America, Europe and Africa, the mobility patterns in Latin America are not well quantified and require further study.