State by state implementation of Zika virus testing guidance in the United States in 2017 and 2018.

In 2015 and 2016, outbreaks of the Zika virus began occurring in the Americas and the Caribbean. Following the introduction of this new threat, the United States' Centers for Disease Control and Prevention (CDC) issued testing guidance for the nation's state public health laboratories. We collected and analyzed testing guidance for all fifty states and the District of Columbia for both 2017 and 2018. In both years, state testing guidance was consistent for men and non-pregnant women, but there was notable variation in guidance for pregnant women. In addition, there were changes between the two years as testing algorithms shifted toward guidance that recommended testing in more limited circumstances. States adopted large, or complete, portions of CDC testing guidance, but were not required to conform completely, 33% of states had identical guidance in 2017 and 49% in 2018. Some of these trends, such as specifying that testing be contingent on travel, or sexual contact with an individual who has recently traveled, to an area where the Zika virus was circulating, presents a potential deficiency in the United States surveillance capacity. Understanding variations in state testing guidance enables public health professionals to better understand ongoing surveillance. This analysis provides insight into the testing practices for the various states across the country. Better understanding of how states approach Zika testing, and how that testing changes over time, will increase the public health community's ability to interpret future Zika case counts.