COCA Partner Notice: Four Recent Zika Publications

December 19, 2016

There have been multiple CDC publications recently related to Zika virus. Keeping up to date on new research and guidance is critical in responding to this emerging health threat. We encourage you to review the four publications below and disseminate this information to your organization’s members.

In a new report published in the Journal of the American Medical Association, CDC scientists used preliminary data from the US Zika Pregnancy Registry (USZPR) to estimate that 6% of completed pregnancies in women with laboratory evidence of possible recent Zika virus infection had birth defects potentially related to Zika virus. The report included data from the continental United States and Hawaii, collected in collaboration between CDC and state and local health departments to monitor pregnancies and fetal or infant outcomes among pregnant women with laboratory evidence of Zika virus infection. This is the first release of preliminary findings based on data reported to the USZPR. Key findings include:

    • Among women with maternal symptoms or laboratory evidence of possible Zika virus infection in the first trimester of pregnancy, birth defects were reported in 11% of completed pregnancies.
    • The proportion of pregnancies with birth defects was similar (around 6%) among pregnant women who experienced symptoms and pregnant women who were asymptomatic.
    • Infants with microcephaly represented 4% of the completed pregnancies, which is substantially higher than the background rate of microcephaly in the United States (7 per 10,000 live births).

Prevention of Zika virus infection during pregnancy is critically important given the severity of its associated birth defects and the preliminary estimates outlined in this report. This report highlights the importance of CDC guidance to test all pregnant women with possible exposure to Zika virus regardless of whether they had symptoms of Zika and to test infants born to women with possible Zika infection during pregnancy. In addition, this report highlights the importance of the USZPR, which collects critical information needed to help us understand the effects of Zika virus infection during pregnancy.

In a new report published in Emerging Infectious Diseases, CDC experts examined the replication and persistence of Zika virus in fetal and infant brain and placental tissue. The study included tissue from pregnancy losses (miscarriage, etc.), negative birth outcomes (babies who had microcephaly and later died), and from placentas from women who had suspected Zika and had babies who appeared healthy or had microcephaly. The authors found:

    • Zika virus can make thousands of copies of itself in fetuses’ brains and in the placentas of pregnant women, which may help explain how the virus causes devastating birth defects and pregnancy losses even if a woman had only mild illness.
    • Zika virus can persist in tissues for seven months in utero and up to two months after birth.

 The findings further support the linkage of Zika virus with microcephaly and suggest its association with adverse pregnancy outcomes.

In a new editorial published in the New England Journal of Medicine, CDC experts comment on the findings of a new study, “Zika Virus Infection in Pregnant Women in Rio de Janeiro.” The paper found

    •  Among 20 completed pregnancies with infection in the first trimester, two infants had microcephaly (10%) and others had indications of brain abnormalities consistent with the CDC surveillance case definition. Although high proportions of infants had findings noted on imaging, the clinical significance of some findings remains unclear.
    • Damage to the fetal brain can occur even during the second and third trimesters.

These findings emphasize the urgency of planning for the needs of children and families affected by congenital Zika syndrome.

The authors of the editorial explain how the outbreak of Zika virus in the Americas has highlighted the challenges in adequately monitoring and documenting adverse health effects on fetuses and infants following prenatal infection. They also discuss how the current outbreak emphasizes the importance of birth defects surveillance programs to evaluate prevention efforts.

On November 28, 2016, the Texas Department of State Health Services (TDSHS) reported the first case of locally acquired mosquito-borne Zika virus infection in the city of Brownsville, Cameron County, Texas. On December 9, 2016, four additional cases in people living in proximity to the first case were reported. TDSHS continues to investigate Zika virus transmission in Brownsville. The exact level and location of risk of Zika virus infection in Brownsville is unknown; pregnant women in the area are at some risk for Zika virus infection.

For these reasons, CDC is designating the city of Brownsville as a Zika cautionary (yellow) area for testing and travel guidance, as recommended in the CDC Interim Zika Response Plan. Pregnant women who live in other areas should consider postponing travel to Brownsville. Areas of mosquito-borne transmission can arise and resolve over time. Travelers, and in particular, pregnant women, are urged to monitor the CDC website to ensure they have access to the most up-to-date information and recommendations.

If you have questions about this reminder or have other clinical questions, please email us at

On behalf of the Clinician Outreach and Communication Activity (COCA)
Centers for Disease Control and Prevention (CDC)
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