Underscoring the serious risk of birth defects from Zika, federal health officials on Tuesday reported that about one in 10 pregnant women with a confirmed infection in 2016 had a fetus or baby with a brain abnormality or other neurological disorder associated with the virus.
The risk for birth defects from Zika was even higher, about 15 percent, among mothers infected during the first trimester of pregnancy, according to the Centers for Disease Control and Prevention’s latest “Vital Signs” report.
“Zika continues to be a threat to pregnant women in the United States,” said CDC Acting Director Anne Schuchat in a conference call with reporters on Tuesday. “With warm weather, a new mosquito season and summer travel rapidly approaching, prevention is crucial to protect the health of mothers and babies.”
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The CDC report confirms earlier findings that Zika during pregnancy can cause babies and fetuses to develop brain abnormalities such as microcephaly, eye disorders, central nervous system dysfunction and other neurological problems.
The report is based on outcomes for the largest number of pregnancies with confirmed Zika infection to date in the continental United States, as reported to the U.S. Zika Pregnancy Registry from Jan. 15 to Dec. 27, 2016.
During that time, 1,297 pregnant women in 44 states were reported to the registry, but only 972 completed their pregnancies, live births and stillborn, in the time frame analyzed.
Among the 972 completed pregnancies, Zika-related birth defects were reported in 51, or 5 percent. But the proportion of birth defects was higher, about 10 percent, when limited to pregnancies with laboratory-confirmed infections.
10% Ratio of pregnant women with Zika who had baby or fetus with birth defect in 2016
The distinction shows the complexity of Zika testing. There is only a narrow time frame, about two weeks after symptoms begin, to obtain a positive lab result that detects virus molecules in the blood or urine.
After that time, Zika tests can only detect antibodies developed by the immune system to fight the virus — but those tests cannot clearly distinguish between antibodies for Zika and related pathogens, such as dengue and chikungunya, which requires further testing.
In addition, most people infected with Zika, about four out of five, do not have symptoms, which can include fever, muscle pain, rash and red eyes.
For that reason, the CDC is monitoring all pregnant women with any evidence of recent Zika infection. Schuchat said the Zika pregnancy registry is growing fast and currently counts more than 1,600 cases in the 50 states and Washington, D.C.
“We’re still seeing about 30 to 40 new Zika cases in pregnant women each week in the Untied States,” she said.
The report also emphasizes the need for better monitoring of babies born to mothers who had Zika during pregnancy, said Peggy Honein, co-leader for the CDC Zika Response Team’s Pregnancy and Birth Defects Task Force.
Only about one in four children born to mothers with Zika last year in the United States received brain imaging as recommended by the CDC. Without brain scans and other recommended follow-up care, she said, it’s possible that the rate of Zika-related birth defects is higher than reported.
“We know that some babies have underlying brain defects that are otherwise not evident at birth,” Honein said. “Because we do not have brain imaging reports for most infants whose mothers had Zika during pregnancy, our current report might significantly underestimate the impact of Zika.”
Zika is spread primarily through the bite of an infected Aedes aegytpi and Aedes albopictus species mosquito. The virus also can spread from mother to child, through sex and through blood transfusions.
She said some babies born to mothers who had Zika while pregnant develop microcephaly after they’re born, while others have vision loss or difficulty hearing. Some are unable to extend their limbs, she said, while others miss developmental milestones, such as sitting up independently by four to seven months of age.
The costs of caring for a baby born with microcephaly can be financially crippling for families and for public health resources. Schuchat said the cost of treating an infant with microcephaly is estimated at nearly $4 million. “For those who survive into adulthood,” she said, “the cost can be up to $10 million.”
Honein said the numbers show an undeniable increase in microcephaly and related neurological defects in the United States. The rate of 10 percent reported in 2016 is more than 30 times higher than the baseline prevalence in prior years, when the rate was about three of every 1,000 live births.
“Prevention is key,” Honein said. “There are basic steps people, and especially pregnant women and their male partners, can take to help protect themselves from Zika.”
In the 51 cases of birth defects documented by the CDC report, the mothers were exposed to Zika in 16 countries or U.S. territories with active spread of the virus, including Barbados, Belize, Brazil, Cape Verde, Colombia, Dominican Republic, El Salvador, Guatemala, Guyana, Haiti, Honduras, Jamaica, Mexico, Puerto Rico, Republic of Marshall Islands and Venezuela.
However, the CDC analysis does not include data from pregnant women in Puerto Rico, where more than 37,000 cases have been reported since 2015, because the U.S. territorial island has its own Zika pregnancy registry.
CDC guidance advises pregnant women to stay away from any areas with risk of Zika, including Miami-Dade, where state health officials in 2016 identified four areas with active spread of the virus, including Miami’s Wynwood and Little River neighborhoods, and most of Miami Beach.
In addition, a number of cases were reported in Miami-Dade in 2016 with no identified area of exposure — leading the CDC to report in March that the threat of Zika was even greater for South Florida than previously understood, with a heightened risk since June 2016 for residents in Broward and Palm Beach counties because of local travel patterns and challenges in identifying all areas where the virus was spreading.
Prevention is key.
Peggy Honein, Centers for Disease Control and Prevention
Schuchat said the CDC will not report individual state results from the national Zika pregnancy registry out of concern for patient privacy. In 2016, Florida health officials confirmed 1,440 Zika infections, including 292 pregnant women.
This year, the health department has reported 34 Zika infections statewide, including 18 pregnant women.
Zika has been nearly dormant in Miami-Dade so far in 2017, with two locally acquired cases confirmed and no zones of active transmission identified.
Florida Gov. Rick Scott’s budget proposal calls for new funding for the health department to hire more scientists and conduct more research to combat the spread of Zika, and Philip said in March that the state’s bureau of public labs has “increased capacity greatly” for testing.
She said by mid-April, the state will begin conducting a complex test for distinguishing Zika from related viruses, such as dengue and chikungunya, that previously only the CDC could perform. Philip said having the state conduct the test, known as a plaque reduction neutralization test, will cut wait times from two to three months to several weeks.
Last year, a backlog of Zika test results led to hundreds of patients, most of them pregnant women, waiting months to receive their results.
The CDC had tested 2,107 specimens sent by Florida as of March 15, according to the agency. Philip said that as of March 27, the health department was waiting for the CDC to deliver Zika test results for about 26 cases, including 16 possible infections from 2016 and 10 this year.
In addition to funding more lab resources, Philip said the health department also will launch a program to coordinate care for infants born to mothers infected with Zika while pregnant. She said local hospitals, such as Jackson Health System✔, have established Zika-specific care plans, and that the state agency would help ensure that patients follow CDC guidelines for evaluating infants affected by the virus.