Zika Virus Speed and Direction: Reconstructing Zika Introduction in Brazil

Introduction Local transmission of Zika virus has been confirmed in 67 countries worldwide and in 46 countries or territories in the Americas (1,2). On February 1, 2016 the World Health Organization declared a Public Health Emergency of International Concern due to the increase in microcephaly cases and other neurological disorders reported in Brazil (2). Several countries issued travel warnings for pregnant women travelling to Zika-affected countries with Brazil, Colombia, Ecuador, and El Salvador advising against pregnancy (3-7). The risk of local transmission in unaffected regions is unknown but potentially significant where competent Zika vectors are present (8) and also given the additional complexities of sexual transmission and population mobility (9,10). Despite the rapid spread of Zika virus across the Americas and global concerns regarding its effects on fetuses, little is known about the pattern of spread. Knowledge of the direction and the speed of movement of disease is invaluable for public health response planning, including the timing and placement of interventions.