This report launches the weekly reporting of pregnant women with laboratory evidence of possible Zika virus infection in U.S. states and territories. Monitoring all pregnant women with possible Zika virus infection during pregnancy, whether asymptomatic or symptomatic, will enhance understanding of possible adverse outcomes and allow better estimates of the number of pregnancies at risk for adverse outcomes. This information will assist health care providers who counsel pregnant women and will facilitate planning services for affected families.

In February 2016, CDC, in collaboration with state, local, tribal, and territorial health departments, launched comprehensive surveillance systems to report and actively monitor pregnancies and congenital outcomes among symptomatic and asymptomatic women with laboratory evidence of possible Zika virus infection. As of May 12, 2016, there were 157 and 122 pregnant women with laboratory evidence of possible Zika virus infection residing in U.S. states and U.S. territories, respectively.

Zika virus is a cause of microcephaly and brain abnormalities (1), and it is the first known mosquito-borne infection to cause congenital anomalies in humans. The establishment of a comprehensive surveillance system to monitor pregnant women with Zika virus infection will provide data to further elucidate the full range of potential outcomes for fetuses and infants of mothers with asymptomatic and symptomatic Zika virus infection during pregnancy. In February 2016, Zika virus disease and congenital Zika virus infections became nationally notifiable conditions in the United States (2). Cases in pregnant women with laboratory evidence of Zika virus infection who have either 1) symptomatic infection or 2) asymptomatic infection with diagnosed complications of pregnancy can be reported as cases of Zika virus disease to ArboNET* (2), CDC’s national arboviral diseases surveillance system. Under existing interim guidelines from the Council for State and Territorial Epidemiologists (CSTE), asymptomatic Zika virus infections in pregnant women who do not have known pregnancy complications are not reportable. ArboNET does not currently include pregnancy surveillance information (e.g., gestational age or pregnancy exposures) or pregnancy outcomes. To understand the full impact of infection on the fetus and neonate, other systems are needed for reporting and active monitoring of pregnant women with laboratory evidence of possible Zika virus infection during pregnancy. Thus, in collaboration with state, local, tribal, and territorial health departments, CDC established two surveillance systems to monitor pregnancies and congenital outcomes among women with laboratory evidence of Zika virus infection† in the United States and territories: 1) the U.S. Zika Pregnancy Registry (USZPR),§ which monitors pregnant women residing in U.S. states and all U.S. territories except Puerto Rico, and 2) the Zika Active Pregnancy Surveillance System (ZAPSS), which monitors pregnant women residing in Puerto Rico. As of May 12, 2016, the surveillance systems were monitoring 157 and 122 pregnant women with laboratory evidence of possible Zika virus infection from participating U.S. states and territories, respectively. Tracking and monitoring clinical presentation of Zika virus infection, all prenatal testing, and adverse consequences of Zika virus infection during pregnancy are critical to better characterize the risk for congenital infection, the performance of prenatal diagnostic testing, and the spectrum of adverse congenital outcomes. These data will improve clinical guidance, inform counseling messages for pregnant women, and facilitate planning for clinical and public health services for affected families.

Zika virus disease and congenital Zika virus infection are defined by the interim CSTE case definition and include confirmed and probable cases with laboratory evidence of infection (2). The clinical criteria for Zika virus disease include the presence of one of four symptoms (fever, rash, arthralgia, and conjunctivitis), or Guillain-Barré syndrome, or an adverse pregnancy outcome (fetal loss, or in utero findings of microcephaly or intracranial calcifications) in a symptomatic or asymptomatic mother with compatible illness or epidemiologic risk factors for Zika virus infection. Clinical criteria for Zika virus congenital infection in infants include microcephaly, intracranial calcifications, or other central nervous system abnormalities (2). Jurisdictions report cases meeting these criteria to ArboNET. Although jurisdictions can report asymptomatic infection in pregnant women without pregnancy complications to ArboNET, this reporting is at the discretion of the local jurisdiction and is not universal. Current ArboNET reporting includes cases of Zika virus disease that meet the interim CSTE case definition.

For the purposes of the USZPR and ZAPSS, laboratory evidence of possible Zika virus infection is defined as a positive Zika virus real-time reverse transcription–polymerase chain reaction (rRT-PCR) test result (i.e., a confirmed case of Zika virus infection) or an equivocal or presumptive positive Zika virus immunoglobulin M (IgM) antibody capture enzyme-linked immunosorbent assay (ELISA) test result (3–5).¶ Plaque reduction neutralization testing (PRNT) performed in conjunction with the IgM ELISA must have Zika PRNT titers ≥10 for inclusion. Pregnant women who meet laboratory criteria are included in the surveillance systems whether they report symptoms or not. Women are included retrospectively if laboratory evidence of congenital Zika virus infection is identified in fetal tissues, the placenta, or the infant.

The USZPR was initiated primarily to monitor outcomes in pregnant women returning from travel to areas with local Zika virus transmission (6). To date the majority of cases in pregnant women reported to USZPR are associated with travel, but it also includes cases of sexual transmission (7) and local transmission from the U.S. territories. ZAPSS was developed separately for Puerto Rico to conduct enhanced surveillance in pregnant women at risk for Zika virus infection as a result of ongoing local Zika virus transmission. Using USZPR and ZAPSS, CDC will report the number of pregnant women with laboratory evidence of possible Zika virus infection weekly on its website. Data reported by noon Eastern Standard Time each Thursday (for this report, May 12, 2016) will be verified and reported in aggregate the following Thursday. Reporting is subject to a lag of 1 week to verify data from each participating jurisdiction. Reports from Arizona and Idaho have not yet been verified and are excluded from the current report.

As of May 12, 2016, combined data from USZPR and ZAPSS include 279 reports of pregnant women with laboratory evidence of possible Zika virus infection, including 157 pregnant women residing in U.S. states and the District of Columbia (Figure 1) and 122 residing in U.S. territories (Figure 2). As of May 11, 2016, 113 pregnant women meeting clinical criteria for Zika virus disease were reported to CDC through ArboNET, 48 in U.S. states, and 65 in U.S. territories.

Among the 157 pregnant women from U.S. states and the District of Columbia monitored through USZPR, 73 (49%)** reported clinical symptoms consistent with Zika virus disease. Among these symptomatic pregnant women, 64 (88%) reported rash, 36 (49%) arthralgia, 37 (51%) fever, and 17 (23%) conjunctivitis. Among all pregnancies included from U.S. states, Zika virus nucleic acid detection by rRT-PCR was reported in 39 (25%).

Among 122 pregnant residents of the U.S. territories†† being monitored in USZPR or ZAPSS, 80 (66%)§§ reported clinical symptoms consistent with Zika virus disease. Among these symptomatic women, 60 (75%) reported rash, 29 (36%) arthralgia, 27 (34%) fever, and 15 (19%) conjunctivitis. Among all women included from U.S. territories, Zika virus nucleic acid detection by rRT-PCR in serum was identified in 67 (55%).