@article{Zinszer_Morrison_Brownstein_Marinho_Alexandre_Nsoesie_2017, title={Zika Virus Speed and Direction: Reconstructing Zika Introduction in Brazil}, volume={9}, url={https://ojphi.org/ojs/index.php/ojphi/article/view/7709}, DOI={10.5210/ojphi.v9i1.7709}, abstractNote={<div style="left: 72px; top: 284.606px; font-size: 11.3333px; font-family: sans-serif; transform: scaleX(1.08137);" data-canvas-width="51.022666666666666">Objective</div><div style="left: 84px; top: 296.567px; font-size: 11.3333px; font-family: serif; transform: scaleX(0.977042);" data-canvas-width="302.41073333333316">To estimate the velocity of Zika virus disease spread in Brazil using</div><div style="left: 72px; top: 309.901px; font-size: 11.3333px; font-family: serif; transform: scaleX(1.00432);" data-canvas-width="298.3839999999998">data on confirmed Zika virus disease cases at the municipal-level.</div><div style="left: 72px; top: 335.273px; font-size: 11.3333px; font-family: sans-serif; transform: scaleX(1.11794);" data-canvas-width="66.10733333333333">Introduction</div><div style="left: 84px; top: 347.234px; font-size: 11.3333px; font-family: serif; transform: scaleX(1.10593);" data-canvas-width="307.2285333333332">Local transmission of Zika virus has been confirmed in</div><div style="left: 72px; top: 360.567px; font-size: 11.3333px; font-family: serif; transform: scaleX(0.997909);" data-canvas-width="316.753066666667">67 countries worldwide and in 46 countries or territories in the</div><div style="left: 72px; top: 373.901px; font-size: 11.3333px; font-family: serif; transform: scaleX(1.00298);" data-canvas-width="50.082">Americas (</div><div style="left: 122.079px; top: 373.901px; font-size: 11.3333px; font-family: serif;">1</div><div style="left: 127.746px; top: 373.901px; font-size: 11.3333px; font-family: serif;">,</div><div style="left: 130.579px; top: 373.901px; font-size: 11.3333px; font-family: serif;">2</div><div style="left: 136.246px; top: 373.901px; font-size: 11.3333px; font-family: serif; transform: scaleX(1.00785);" data-canvas-width="250.63666666666666">). On February 1, 2016 the World Health Organization</div><div style="left: 72px; top: 387.234px; font-size: 11.3333px; font-family: serif; transform: scaleX(1.00764);" data-canvas-width="315.0066">declared a Public Health Emergency of International Concern due to</div><div style="left: 72px; top: 400.567px; font-size: 11.3333px; font-family: serif; transform: scaleX(1.02464);" data-canvas-width="315.65713333333326">the increase in microcephaly cases and other neurological disorders</div><div style="left: 72px; top: 413.901px; font-size: 11.3333px; font-family: serif; transform: scaleX(1.04645);" data-canvas-width="90.3606666666667">reported in Brazil (</div><div style="left: 162.308px; top: 413.901px; font-size: 11.3333px; font-family: serif;">2</div><div style="left: 168.04px; top: 413.901px; font-size: 11.3333px; font-family: serif; transform: scaleX(1.04429);" data-canvas-width="219.78733333333335">). Several countries issued travel warnings for</div><div style="left: 72px; top: 427.234px; font-size: 11.3333px; font-family: serif; transform: scaleX(0.978546);" data-canvas-width="316.0866666666668">pregnant women travelling to Zika-affected countries with Brazil,</div><div style="left: 72px; top: 440.567px; font-size: 11.3333px; font-family: serif; transform: scaleX(0.999316);" data-canvas-width="316.7666666666666">Colombia, Ecuador, and El Salvador advising against pregnancy</div><div style="left: 72px; top: 453.901px; font-size: 11.3333px; font-family: serif;">(</div><div style="left: 75.764px; top: 453.901px; font-size: 11.3333px; font-family: serif;">3</div><div style="left: 81.4205px; top: 453.901px; font-size: 11.3333px; font-family: serif;">-</div><div style="left: 85.1845px; top: 453.901px; font-size: 11.3333px; font-family: serif;">7</div><div style="left: 90.8412px; top: 453.901px; font-size: 11.3333px; font-family: serif; transform: scaleX(0.984769);" data-canvas-width="295.5619999999999">). The risk of local transmission in unaffected regions is unknown</div><div style="left: 72px; top: 467.234px; font-size: 11.3333px; font-family: serif; transform: scaleX(1.01696);" data-canvas-width="315.29106666666667">but potentially significant where competent Zika vectors are present</div><div style="left: 72px; top: 480.567px; font-size: 11.3333px; font-family: serif;">(</div><div style="left: 75.7741px; top: 480.567px; font-size: 11.3333px; font-family: serif;">8</div><div style="left: 81.4408px; top: 480.567px; font-size: 11.3333px; font-family: serif; transform: scaleX(1.00469);" data-canvas-width="305.4922666666667">) and also given the additional complexities of sexual transmission</div><div style="left: 72px; top: 493.901px; font-size: 11.3333px; font-family: serif; transform: scaleX(0.995557);" data-canvas-width="123.24999999999997">and population mobility (</div><div style="left: 195.18px; top: 493.901px; font-size: 11.3333px; font-family: serif;">9</div><div style="left: 200.969px; top: 493.901px; font-size: 11.3333px; font-family: serif;">,</div><div style="left: 203.925px; top: 493.901px; font-size: 11.3333px; font-family: serif; transform: scaleX(1.022);" data-canvas-width="11.582666666666665">10</div><div style="left: 215.503px; top: 493.901px; font-size: 11.3333px; font-family: serif; transform: scaleX(0.974952);" data-canvas-width="173.07019999999994">). Despite the rapid spread of Zika</div><div style="left: 72px; top: 507.234px; font-size: 11.3333px; font-family: serif; transform: scaleX(1.03356);" data-canvas-width="315.3749333333333">virus across the Americas and global concerns regarding its effects</div><div style="left: 72px; top: 520.567px; font-size: 11.3333px; font-family: serif; transform: scaleX(1.00864);" data-canvas-width="315.0304">on fetuses, little is known about the pattern of spread. Knowledge of</div><div style="left: 72px; top: 533.901px; font-size: 11.3333px; font-family: serif; transform: scaleX(1.01337);" data-canvas-width="315.12333333333333">the direction and the speed of movement of disease is invaluable for</div><div style="left: 72px; top: 547.234px; font-size: 11.3333px; font-family: serif; transform: scaleX(1.00913);" data-canvas-width="315.0995333333333">public health response planning, including the timing and placement</div><div style="left: 72px; top: 560.567px; font-size: 11.3333px; font-family: serif; transform: scaleX(1.00256);" data-canvas-width="74.29">of interventions.</div><div style="left: 72px; top: 585.94px; font-size: 11.3333px; font-family: sans-serif; transform: scaleX(1.07312);" data-canvas-width="46.59133333333333">Methods</div><div style="left: 84px; top: 597.901px; font-size: 11.3333px; font-family: serif; transform: scaleX(0.991744);" data-canvas-width="304.6966666666666">Data for this analysis were obtained from the Brazil Ministry</div><div style="left: 72px; top: 611.234px; font-size: 11.3333px; font-family: serif; transform: scaleX(0.964385);" data-canvas-width="316.1093333333334">of Health and consisted of confirmed cases of Zika virus disease.</div><div style="left: 72px; top: 624.567px; font-size: 11.3333px; font-family: serif; transform: scaleX(0.95756);" data-canvas-width="315.8350666666667">The centroids of the municipalities were taken in meters from the</div><div style="left: 72px; top: 637.901px; font-size: 11.3333px; font-family: serif; transform: scaleX(0.994998);" data-canvas-width="316.7077333333333">shapefiles and used to perform a surface trend analysis. Surface</div><div style="left: 72px; top: 651.234px; font-size: 11.3333px; font-family: serif; transform: scaleX(1.04518);" data-canvas-width="315.7829333333332">trend is a spatial interpolation method used to estimate continuous</div><div style="left: 72px; top: 664.567px; font-size: 11.3333px; font-family: serif; transform: scaleX(1.00473);" data-canvas-width="314.9340666666666">surfaces from point data. The continuous surface of time to infection</div><div style="left: 72px; top: 677.901px; font-size: 11.3333px; font-family: serif; transform: scaleX(0.995817);" data-canvas-width="314.6450666666666">was estimated by regressing it against the X and Y coordinates. Time</div><div style="left: 72px; top: 691.234px; font-size: 11.3333px; font-family: serif; transform: scaleX(1.01863);" data-canvas-width="315.2842666666666">was in days and X and Y coordinates were meters. Parameters were</div><div style="left: 72px; top: 704.567px; font-size: 11.3333px; font-family: serif; transform: scaleX(1.0012);" data-canvas-width="314.8116666666666">estimated using least squares regression and velocity (in km per day)</div><div style="left: 72px; top: 717.901px; font-size: 11.3333px; font-family: serif; transform: scaleX(1.00446);" data-canvas-width="266.93399999999997">was obtained by inverting the final magnitude of the slope.</div><div style="left: 72px; top: 743.273px; font-size: 11.3333px; font-family: sans-serif; transform: scaleX(1.08488);" data-canvas-width="40.93600000000001">Results</div><div style="left: 84px; top: 755.234px; font-size: 11.3333px; font-family: serif; transform: scaleX(0.975156);" data-canvas-width="304.31359999999995">Data provided from the Brazil Ministry of Health on May 31,</div><div style="left: 72px; top: 768.567px; font-size: 11.3333px; font-family: serif; transform: scaleX(0.956072);" data-canvas-width="316.0934666666666">2016, indicated that Zika had been confirmed in 316 of the 5,564</div><div style="left: 72px; top: 781.901px; font-size: 11.3333px; font-family: serif; transform: scaleX(0.972513);" data-canvas-width="316.1478666666666">municipalities in Brazil representing 26 states, with six additional</div><div style="left: 72px; top: 795.234px; font-size: 11.3333px; font-family: serif; transform: scaleX(0.969219);" data-canvas-width="315.7716">municipalities identified from other reporting sources. Our models</div><div style="left: 72px; top: 808.567px; font-size: 11.3333px; font-family: serif; transform: scaleX(1.03815);" data-canvas-width="315.6310666666668">indicated a southward pattern of introduction of Zika starting from</div><div style="left: 72px; top: 821.901px; font-size: 11.3333px; font-family: serif; transform: scaleX(1.0215);" data-canvas-width="315.3896666666665">the northeast coast towards the southeastern coastal states of Rio de</div><div style="left: 72px; top: 835.234px; font-size: 11.3333px; font-family: serif; transform: scaleX(1.03922);" data-canvas-width="315.6967999999999">Janerio, Espírito Santo, and São Paulo. There was also a pattern of</div><div style="left: 72px; top: 848.567px; font-size: 11.3333px; font-family: serif; transform: scaleX(0.966796);" data-canvas-width="315.9166666666668">western movement towards Bolivia. Overall, the average speed of</div><div style="left: 72px; top: 861.901px; font-size: 11.3333px; font-family: serif; transform: scaleX(0.951843);" data-canvas-width="315.78973333333346">diffusion was 42.1 km/day across all models was 6.9 km/day to a</div><div style="left: 72px; top: 875.234px; font-size: 11.3333px; font-family: serif; transform: scaleX(1.01805);" data-canvas-width="315.2729333333333">maximum of 634.1 km/day. The municipalities in the Northeast and</div><div style="left: 72px; top: 888.567px; font-size: 11.3333px; font-family: serif; transform: scaleX(1.03167);" data-canvas-width="315.6741333333332">North regions had the slowest speeds whereas the municipalities in</div><div style="left: 72px; top: 901.901px; font-size: 11.3333px; font-family: serif; transform: scaleX(1.01288);" data-canvas-width="315.1063333333333">the Central-West and Southeast regions had the highest speeds. This</div><div style="left: 72px; top: 915.234px; font-size: 11.3333px; font-family: serif; transform: scaleX(0.978265);" data-canvas-width="314.39800000000014">is due to proximity of cases in time and space, with more cases having</div><div style="left: 72px; top: 928.567px; font-size: 11.3333px; font-family: serif; transform: scaleX(0.994303);" data-canvas-width="314.64733333333334">occurred closer in time and over larger areas in South, Southeast, and</div><div style="left: 72px; top: 941.901px; font-size: 11.3333px; font-family: serif; transform: scaleX(1.00569);" data-canvas-width="276.36333333333323">Central-West regions resulting in faster rates of introduction.</div><div style="left: 408px; top: 284.606px; font-size: 11.3333px; font-family: sans-serif; transform: scaleX(1.10259);" data-canvas-width="68.01133333333334">Conclusions</div><div style="left: 420px; top: 296.567px; font-size: 11.3333px; font-family: serif; transform: scaleX(0.989304);" data-canvas-width="304.7714666666668">The average speed of spread was 42 km per day and it took</div><div style="left: 408px; top: 309.901px; font-size: 11.3333px; font-family: serif; transform: scaleX(1.03146);" data-canvas-width="317.6551999999999">approximately five to six months for Zika to spread from the</div><div style="left: 408px; top: 323.234px; font-size: 11.3333px; font-family: serif; transform: scaleX(0.961511);" data-canvas-width="315.98466666666684">northeastern coast to the southeastern coast and western border of</div><div style="left: 408px; top: 336.567px; font-size: 11.3333px; font-family: serif; transform: scaleX(1.02575);" data-canvas-width="315.469">Brazil. The rapid spread of Zika can help us understand its possible</div><div style="left: 408px; top: 349.901px; font-size: 11.3333px; font-family: serif; transform: scaleX(1.03363);" data-canvas-width="315.6367333333334">future directions and the pace at which it travels, which are key for</div><div style="left: 408px; top: 363.234px; font-size: 11.3333px; font-family: serif; transform: scaleX(0.9898);" data-canvas-width="314.4263333333333">targeted mosquito control interventions, public health messaging, and</div><div style="left: 408px; top: 376.567px; font-size: 11.3333px; font-family: serif; transform: scaleX(0.978794);" data-canvas-width="314.48639999999995">travel advisories. A multi-country analysis is needed to understand the</div><div style="left: 408px; top: 389.901px; font-size: 11.3333px; font-family: serif; transform: scaleX(1.00218);" data-canvas-width="309.7399999999999">continental spatial and temporal patterns of dispersion of Zika virus.</div>}, number={1}, journal={Online Journal of Public Health Informatics}, author={Zinszer, Kate and Morrison, Kathryn and Brownstein, John S. and Marinho, Fatima and Alexandre, Santos F. and Nsoesie, Elaine O.}, year={2017}, month={May} }