Although the likelihood of Zika virus infection is low among asymptomatic patients, the Centers for Disease Control and Prevention recommends offering Zika virus testing to asymptomatic pregnant women with potential exposure.

The recommendation is based on Zika virus testing performed in U.S. states and the District of Columbia from Jan. 3 to March 5, 2016. The analysis included specimens that were received for testing at the CDC Arboviral Diseases Branch and confirmed Zika virus infection was defined as detection of Zika virus RNA by reverse transcription-polymerase chain reaction, or anti-Zika immunoglobulin M antibodies by enzyme-linked immunosorbent assay with neutralizing antibody titers against Zika virus, at levels greater than or equal to fourfold higher than those against dengue virus.

A total of 4,534 patients were tested: 3,335 (74%) were pregnant women. Among 1,541 patients with one or more Zika virus–associated symptoms, 182 (12%) had confirmed Zika virus infection. Only seven (0.3%) of 2,425 asymptomatic pregnant women who were tested had confirmed Zika virus infection. Of those patients, five resided in areas with active Zika virus transmission at some time during their pregnancy and two were short-term travelers, according to Dr. Sarah Reagan-Steiner of the CDC’s National Center for Immunization and Respiratory Diseases and her coauthors.

“It is reassuring that the proportion of asymptomatic pregnant women with confirmed Zika virus infection in this report was low” and not unexpected in the current U.S. setting, where most exposure to the Zika virus is travel-associated, Dr. Reagan-Steiner and her coauthors wrote.

No conflicts of interested were reported by the authors. Read the full report in MMWR (Morb Mortal Wkly Rep. 2016 Apr 15. doi: 10.15585/mmwr.mm6515e1).

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