409 specimens from July 14 to December 14, 2016, that had previously been deemed negative for Zika have had to be re-tested by the Centers for Disease Control and Prevention (CDC) or CDC-approved labs. Doctors offices, hospitals, clinics, and other healthcare organizations in the Washington, DC, area have been sending specimens to the Public Health Laboratory for testing, in the specified interval but an error occurred. Of the 409 specimens, 294 were from pregnant women. A mistake on a test could dramatically alter the course of lives blocking time-sensitive decisions. It’s just what happened. Results for all retested specimens are expected within three to four weeks. The District appears to be the only jurisdiction in the country with this problem, CDC officials said. They described the error linked to a complicated test that involved multiple calculations and said the problem was essentially a math mistake.