The number of pregnant women in the US with the Zika virus is going up as the Centers for Disease Control and Prevention (CDC) reevaluates how it reports cases.
Previously, pregnant women with an asymptomatic Zika virus infection who do not have known pregnancy complications were not reportable. However, the CDC established new surveillance systems to monitor pregnancies and congenital outcomes among women with laboratory evidence of Zika infections but no symptoms.
As of May 12, 157 pregnant women in US states and 122 pregnant women in US territories were being monitored for evidence of possible Zika virus infection. These systems are monitoring clinical presentation of the infection, all prenatal testing, and adverse consequences of the virus during pregnancy in order to better understand the risk for congenital infection 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,” according to the CDC’s Morbidity and Mortality Weekly Report.
The criteria for the Zika virus among asymptomatic or symptomatic pregnant women include the presence of fever, rash, arthralgia, or conjunctivitis, Guillain-Barré syndrome, or an adverse pregnancy outcome, such as fetal loss or in utero findings of microcephaly. The clinical criteria for Zika virus congenital infection in infants include microcephaly, intracranial calcifications, or other central nervous system abnormalities.
Among the 157 women in the states being monitored, only 49% reported clinical symptoms consistent with Zika virus and among the 122 pregnant women in the US territories, 66% reported clinical symptoms.
“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,” according to the report.
However, the expanded definition being used can also overestimate Zika virus infection among pregnant women being screened because of crossreactivity with dengue and other, similar viruses.
“Findings from these U.S. surveillance systems are expected to improve understanding of Zika virus infection during pregnancy, enhance risk assessment and counseling of pregnant women and families, advance clinical care, and assist states and territories to anticipate and plan needed resources and increase prevention efforts,” the report concluded.