Surveillance Systems Offer Early Numbers on Zika in Pregnant Women

May 26, 2016 04:45 pm News Staff

As previously reported by AAFP News, the CDC -- in collaboration with state, local, tribal and territorial health departments -- established two enhanced surveillance systems earlier this spring to report and actively monitor pregnancies and congenital outcomes among symptomatic and asymptomatic women with laboratory evidence of possible Zika virus infection. Health officials anticipate that these surveillance activities will contribute to a better understanding of the full impact of Zika virus infection on pregnant women and their unborn fetuses.

[Pregnant woman sitting in chair]

On May 20, the CDC released a Morbidity and Mortality Weekly Report (MMWR)(www.cdc.gov) the first in what is to be a series of weekly reports from the pair of surveillance systems: the U.S. Zika Pregnancy Registry (USZPR), which monitors pregnant women residing in U.S. states and all territories except Puerto Rico, and the Zika Active Pregnancy Surveillance System (ZAPSS), which monitors pregnant women who reside in Puerto Rico.

According to the MMWR report, as of May 12, the two surveillance systems were monitoring 157 and 122 pregnant women with laboratory evidence of possible Zika virus infection in the United States and U.S. territories, respectively.

In a related media statement,(www.cdc.gov) the CDC said the new numbers reflect a broader group of pregnant women than was previously reported -- now including all pregnant women who have any laboratory evidence of possible Zika virus infection, regardless of whether or not they recalled having symptoms.

Story highlights
  • On May 20, the CDC released a Morbidity and Mortality Weekly Report featuring information from a pair of recently established surveillance systems monitoring Zika virus in the United States and its territories.
  • As of May 12, the two Zika surveillance systems were monitoring 157 pregnant women in the United States and 122 pregnant women in the U.S. territories with laboratory evidence of possible Zika virus infection.
  • In a related media statement, the CDC said the new numbers reflect a broader group of pregnant women than was previously reported -- now including all pregnant women with laboratory evidence of possible Zika virus infection, regardless of whether or not they recalled having symptoms.

"This new way of reporting numbers aligns with recommendations for ongoing monitoring of pregnancies at risk for poor outcomes associated with Zika, based on scientists' current understanding of the effects of Zika virus infection during pregnancy," the statement said.

In its MMWR report, the CDC said tracking and monitoring clinical presentation of Zika virus infection, all prenatal testing, and adverse consequences of Zika virus infection during pregnancy will help the agency 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," said the agency.

New Case Definition Criteria

Until May 20, the CDC had reported the number of people with Zika virus disease using a case definition that included only individuals who had positive laboratory test results and had reported symptoms or pregnancy complications consistent with Zika.

However, said the agency in its media statement, recently published reports indicate that some pregnant women with laboratory evidence of a recent Zika infection but no symptoms have delivered infants with microcephaly and other serious brain defects.

According to the MMWR report, 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.

For the two surveillance systems, 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 -- considered a confirmatory result -- or an equivocal or presumptive positive Zika virus immunoglobulin M (IgM) antibody capture enzyme-linked immunosorbent assay (ELISA) test result.

Plaque reduction neutralization testing (PRNT) performed in conjunction with the IgM ELISA must have Zika PRNT titers of 10 or greater to be included.

It's also important to note that women will be included in the registry retrospectively if laboratory evidence of congenital Zika virus infection is identified in fetal tissues, the placenta or the infant.

Preliminary Findings

To date, most cases of Zika infection in pregnant women reported to USZPR are associated with travel, but cases attributed to sexual and local transmission are also included. ZAPSS was developed separately to focus on the ongoing local Zika virus transmission occurring in Puerto Rico.

The CDC will report updated numbers from the two surveillance systems weekly on its website.(www.cdc.gov) Data reported to the agency by noon EDT each Thursday will be verified with participating jurisdictions and reported in aggregate the following Thursday.

For this initial report, of the 157 pregnant women in the states and the District of Columbia monitored through USPZR, 49 percent reported clinical symptoms consistent with Zika virus disease. Of these symptomatic pregnant women, 88 percent reported rash, 51 percent reported fever, 49 percent reported arthralgia and 23 percent reported conjunctivitis. Zika virus nucleic acid detection by rRT-PCR was reported in 25 percent of cases.

Of the 122 pregnant women in the U.S. territories monitored through USZPR and ZAPSS, 66 percent reported clinical symptoms consistent with Zika virus disease. And of these symptomatic pregnant women, 75 percent reported rash, 36 percent reported arthralgia, 34 percent reported fever and 19 percent reported conjunctivitis. Zika virus nucleic acid detection by rRT-PCR was reported in 55 percent of cases.

"The range of health effects linked with Zika infection during pregnancy, as well as how many and which pregnancies may be at risk of poor outcomes, are essential pieces of information for the public health response to the Zika outbreak," said the CDC in its statement.

"This information will help health care providers as they counsel pregnant women affected by Zika and is essential for planning at the federal, state and local levels for clinical, public health and other services needed to support pregnant women and families affected by Zika."

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