Zika Guidance Updated by the CDC
Although there have been far fewer cases of Zika virus infection in 2017, the Centers for Disease Control and Prevention (CDC) said Zika continues to pose a public health threat to pregnant women, and their infants.
Zika cases continue to be reported by many countries around the world.
The CDC released new interim clinical guidance in Morbidity and Mortality Weekly Report (MMWR) for healthcare professionals who care for infants born to mothers with possible Zika virus infection during pregnancy.
The October 20, 2017 MMWR article updates the agency's August 2016 guidance for healthcare professionals:
- For newborns who exhibit birth defects consistent with congenital Zika syndrome, family physicians should monitor for an expanded list of problems, including hydrocephaly and difficulty breathing and swallowing.
- Infants born to mothers with laboratory evidence of possible Zika virus infection during pregnancy who do not appear to have birth defects consistent with congenital Zika syndrome should receive an ophthalmologic examination by age 1 month and a head ultrasound to detect subclinical brain and eye findings.
"There's a lot we still don't know about Zika, so it's very important for us to keep a close eye on these babies as they develop," said CDC Director Brenda Fitzgerald, M.D.
Laboratory testing for Zika virus has a number of limitations, according to the CDC.
Zika virus RNA is only transiently present in body fluids; thus, negative nucleic acid testing (NAT) does not rule out infection.
Serologic testing is affected by timing of sample collection: a negative immunoglobulin M (IgM) serologic test result does not rule out infection because the serum specimen might have been collected before the development of IgM antibodies, or after these antibodies have waned.
Conversely, IgM antibodies might be detectable for months after the initial infection; for pregnant women, this can make it difficult to determine if infection occurred before or during a current pregnancy.
In addition, cross-reactivity of the Zika virus IgM antibody tests with other flaviviruses can result in a false-positive test result, especially in persons previously infected with or vaccinated against a related flavivirus, further complicating interpretation.
Zika experts defined three groups of infants born to mothers with possible exposure to the virus during pregnancy on which to focus, tailoring their recommendations to each group:
- infants with birth defects consistent with congenital Zika syndrome, regardless of the mother's Zika virus test results;
- infants without birth defects consistent with congenital Zika syndrome born to mothers with laboratory evidence of possible Zika virus infection during pregnancy; and
- infants without birth defects consistent with congenital Zika syndrome born to mothers without laboratory evidence of possible Zika virus infection during pregnancy.
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The CDC said it will continue to update its recommendations as new evidence becomes available.