CDC updates Zika testing and management guidelines

The Centers for Disease Control and Prevention (CDC) has updated its guidance on surveillance and management of the Zika virus using new data collected over the past year.

The new guidelines reflect several concerns, one being that an update from July 2017 may have restricted testing too much in order to avoid false-positives that could delay identification of affected infants who don’t display obvious symptoms of infection at birth.

The guidelines also rescind some prior recommendations, such as the need for thyroid screening and hearing screenings at age 4 to 6 months.

“The updated recommendations emphasize that it is important for pediatric healthcare providers to assess risk of congenital Zika virus infection, to communicate closely with obstetrical providers, and to remain alert for any problems that may develop in infants without birth defects born to mothers with possible Zika virus exposure during pregnancy,” says Margaret Honein, PhD, MPH, chief of the Birth Defects Branch at the CDC’s National Center on Birth Defects and Developmental Disabilities in Atlanta, Georgia.

Zika infection rates have fallen in the United States since reporting of the disease became required, but the virus still poses a significant threat, according to the CDC. The CDC first began tracking Zika in 2015, but infection was not nationally notifiable at that time. A total of 61 symptomatic cases were reported in US states in 2015, according to the CDC, but that number jumped to 5102 in 2016 when Zika became a notifiable disease. Another 36,079 cases were reported in US territories in 2016, according to the CDC. Totals for 2017 so far are down to 331 in US states and 583 in US territories, but Honein warns that continued surveillance is still important.

The updated guidance specifically addresses infants by 3 categories based on their risk for infection. The first group is infants with birth defects consistent with congenital Zika syndrome born to mothers with possible virus exposure during pregnancy regardless of the mother’s Zika virus test results. The second group is infants without birth defects consistent with congenital Zika syndrome, but who were born to mothers with laboratory evidence of possible Zika virus infection during pregnancy. The third group is infants without birth defects consistent with congenital Zika syndrome born to mothers with possible virus exposure during pregnancy but without laboratory evidence of Zika virus infection during pregnancy. The guidelines offer specific testing and management recommendations for each group.

All infants born with possible Zika exposure should receive a standard evaluation at birth, as well as at subsequent well visits, according to the guidance. These assessments should include a comprehensive physical assessment, age-appropriate vision screening, newborn hearing screening, and developmental monitoring as appropriate based on risk.

Exposure of women to the Zika virus during pregnancy has been associated with serious brain abnormalities and microcephaly in infants, but conclusive laboratory testing at the time of birth is limited, according to the CDC. The virus is only transiently present in bodily fluids, so nucleic acid testing is unable to completely rule out infection. The efficacy of serologic testing can depend on the timing of the sample collection, and antibody testing may provide false-positive results, the CDC adds.

As a result, the updated guidance recommends that nucleic acid testing be offered as a part of routine obstetric care to any asymptomatic pregnant woman with ongoing Zika exposure, but serologic testing is no longer routinely recommended because of the risk of false-positive results. Zika testing is not routinely recommended for asymptomatic pregnant women who have possible recent, but not ongoing, virus exposure, according to the CDC.

“The new guidance provides updated information on interpreting infant laboratory testing results, as well as a review of the guidance for prenatal diagnosis,” Honein says. “In addition, the recommendations for vision and hearing screening have been updated, and some of the previously recommended screenings-including thyroid screening and hearing screening at age 4 to 6 months-are no longer recommended because of a lack of data on whether these screenings are needed.”

Honein says pediatricians should expect to see more infants born with congenital Zika syndrome in 2017 and beyond, and that they need to stay committed to following those infants to understand the effects of Zika infection and ensure appropriate care and services for those infants and their families.