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Study finds microcephaly can develop after birth in infants born to Zika-infected women; Fla. lifts part of travel warning

Infants diagnosed with Zika who are born to women infected with the virus during pregnancy can develop microcephaly after birth, according to a report published Tuesday by the Centers for Disease Control and Prevention (CDC), the New York Times reports (Belluck, New York Times, 11/22).


The Zika virus is not easily diagnosed, and it does not have a cure or vaccine. The virus is most commonly transmitted by a bite from an infected mosquito, but it can also be spread through sexual activity.

In April, Centers for Disease Control and Prevention (CDC) scientists in a study published in the New England Journal of Medicine confirmed that the Zika virus causes microcephaly and other severe brain defects in fetuses (Women's Health Policy Report, 11/4). Microcephaly is characterized by an abnormally small head and brain (Steenhuysen, Reuters, 11/22).

In a report published in JAMA Pediatrics earlier this month, researchers said they have concluded that Zika infection during pregnancy is linked to a distinct pattern of fetal anomalies, which researchers have termed "congenital Zika syndrome." In that report, the researchers discuss five fetal anomalies that occur either exclusively with Zika infection during pregnancy or occur only rarely with other infections. The five anomalies that make up congenital Zika syndrome include: severe microcephaly, decreased brain tissue with a distinct pattern of calcium deposits that suggest brain damage, damage to the back of the eye, limited range of motion in the joints and excessive muscle tone that restricts movement shortly after delivery.

According to Catherine Spong, an OB-GYN and acting director of the National Institute of Child Health and Human Development, infants born to Zika-infected women will require regular monitoring because certain conditions take several months to surface (Women's Health Policy Report, 11/4).

Latest findings

For the latest CDC report, researchers assessed 13 infants from the Brazilian states of Pernambuco and Ceará, all of whom tested positive for Zika but who had a normal head size at birth (van der Linden et al., Morbidity and Mortality Report, 11/22).

For 11 of the infants, scans conducted in the days or weeks post-birth showed brain damage, although none of them yet presented with microcephaly. In addition, one infant did not show signs of any other Zika-related anomalies at birth, though scans shortly after showed excess fluid and anomalies in the brain, according to study author Cynthia Moore, a clinical geneticist and birth-defects expert for the CDC (New York Times, 11/22).

The researchers found that all of the infants experienced a slowdown in head growth. According to Moore, 11 of them experienced a decline in head growth significant enough for them to later be diagnosed with microcephaly (Sun, "To Your Health," Washington Post, 11/22). CDC noted that because of how measurement were conducted, two of the infants had a head circumference at birth that could have been misclassified as falling in the normal range (Morbidity and Mortality Report, 11/22).

According to the study, many of the infants during their first year showed indicators of congenital Zika syndrome. Vanessa van der Linden, an author of the study and a neuropediatrician at the Association for Assistance of Disabled Children, said the infants who developed microcephaly after birth "presented the same pattern, but less severe" than infants with microcephaly at birth (New York Times, 11/22).

Specifically, the researchers found that 10 of the 13 infants experienced trouble swallowing, nine could not move their hands voluntarily, seven had epilepsy and five showed some degree of irritability (Reuters, 11/22). The infants in the study are not yet old enough for researchers to determine whether the infants have cognitive problems or delays in skills such as speech.

In contrast to many infants born with microcephaly, most of the 13 infants in the study had social interaction skills, such as the ability to smile and make eye contact. Further, eight demonstrated good head control.

Experts and study authors said it was unclear why the infants' brains did not develop in line with age and body size, although it could potentially be related to initial fetal brain damage or the immune system's response to the original Zika infection. According to Van der Linden, the study was not large enough to allow generalizations (New York Times, 11/22).


Denise Jamieson, an OB-GYN who is one of the leaders of CDC's Zika response, said the agency will review guidance about screening infants born to Zika-infected women in light of the latest findings.

According to CDC officials, the findings demonstrate the importance of screening pregnant women for Zika infection, comprehensively evaluating infants born to women infected during pregnancy and continuing to monitor the infants' development over the long term. They added that early brain scans, even among infants with normally sized heads, could help identify any Zika-related brain anomalies during pregnancy.

CDC Director Thomas Frieden said, "This is clear evidence that children can be severely affected even if they didn't have microcephaly at birth." He added, "To me, the major key question we don't have the answer for is this: How affected will infants be who don't have microcephaly" ("To Your Health," Washington Post, 11/22).

Fla., federal officials say part of Miami Beach no longer Zika transmission zone

In related news, federal and state officials on Tuesday announced that a large section of Miami Beach is no longer considered an area of local Zika transmission, USA Today reports (Gomez, USA Today, 11/22).

Officials removed the designation because more than 45 days have passed since the last case of local Zika transmission in the area was reported. According to Reuters, the area of active Zika transmission in Miami Beach is now about 1.5 square miles (Stein, Reuters, 11/22).

Currently, state officials suspect local Zika transmission is still occurring in a section of northern Miami known as Little River as well as the southern point of Miami Beach (USA Today, 11/22).

According to Reuters, CDC has updated its travel guidance for the Miami area. CDC said pregnant women should consider delaying travel to Miami-Dade County and specifically advises pregnant women not to travel to areas in the county that are still considered transmission zones.

Overall, Florida officials reported that the state has had 1,201 cases of Zika, of which 236 were locally acquired (Reuters, 11/22).