It's now been more than a year since the Zika virus gained global attention, sickening a million people in dozens of countries. The epidemic began in early 2015 and was declared a public health emergency by the World Health Organization (WHO) in February 2016. WHO declared an end to that emergency in November 2016, but concerns over Zika have lingered, even as new cases have waned. In this week's episode, we speak with Marcia Castro, associate professor of demography in the Department of Global Health and Population at Harvard Chan School. With Castro's help, we’ll take a look at the lingering impact of Zika, what we’ve learned about the virus, and the likelihood of new cases as we enter summer in the United States.