[While still very early in surveillance, it is hoped that actual pregnancy risk may be lower than previously publicized.]
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.
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 (157) 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 (122), Zika virus nucleic acid detection by rRT-PCR in serum was identified in 67 (55%).
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.
Zika virus infection during pregnancy is a cause of microcephaly and other brain abnormalities (1) and it is the first known mosquito-borne infection to cause congenital anomalies in humans. However, the full range of outcomes of asymptomatic and symptomatic Zika virus infection during pregnancy are not yet well understood.
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)…
…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.
Through the establishment of these pregnancy surveillance systems, CDC, in collaboration with state, local, tribal, and territorial partners, is reporting and actively monitoring pregnant women with laboratory evidence of possible Zika virus infection. These surveillance systems monitor pregnant women at risk for adverse congenital outcomes attributable to possible Zika virus infection. Including pregnant women with laboratory evidence of possible Zika virus infection but without a reported history of symptoms more than doubles the number of pregnancies being monitored, compared with pregnancies meeting the interim CSTE case definition and reported by ArboNET.
Limiting surveillance to symptomatic women with confirmed or probable Zika virus disease or to women already affected by an adverse pregnancy outcome excludes a substantial proportion of women with asymptomatic and possible Zika virus infection during pregnancy. In contrast, the broader case definition used for the USZPR and ZAPSS surveillance systems MIGHT OVERESTIMATE Zika virus infection among women screened for infection because of crossreactivity with dengue and other flaviviruses, particularly among residents of U.S. territories and travelers with a history of prior flavivirus infection or flavivirus vaccination (8), or nonspecific reactivity.
Case reports indicate that fetuses and infants of pregnant women with asymptomatic Zika virus infection MIGHT be at risk for microcephaly and other severe brain defects (9,10). Following pregnant women with laboratory evidence of possible Zika virus infection in the surveillance system, regardless of symptoms, allows better characterization of the full impact and consequences of infection to the mother and her offspring, and MIGHT allow for better stratification of risk for adverse congenital outcomes (1).
CDC MMWR Early Release / May 20, 2016 /65 http://www.cdc.gov/mmwr/volumes/65/wr/mm6520e1.htm?s_cid=mm6520e1_e