1 pregnant woman found to have Zika after DC testing error

FILE-In this Feb. 11, 2016 file photo, Dallas County Mosquito Lab microbiologist Spencer Lockwood sorts mosquitos collected in a trap in Hutchins, Texas, that had been set up in Dallas County near the location of a confirmed Zika virus infection. U.S. health officials have begun enrolling volunteers for critical next-stage testing of an experimental vaccine to protect against Zika, the mosquito-borne virus that can cause devastating birth defects in pregnant women. (AP Photo/LM Otero, File)

WASHINGTON (AP) — District of Columbia officials say one pregnant woman tested positive for the Zika virus after initially being told last year that she had tested negative.

The city had to retest more than 400 samples for Zika after discovering that a scientist had made a math error. The samples were sent to the Centers for Disease Control and Prevention to be retested.

The city’s Department of Forensic Sciences announced Monday that two women and one man who had tested negative have been told that they actually tested positive for Zika. One of the two women was pregnant at the time of the test. Zika can cause severe birth defects, including babies born with abnormally small heads.

The CDC said 394 samples tested negative and results were inconclusive for 26 samples.