Lissencephaly

ATLANTA -- The Centers for Disease Control and Prevention is asking clinicians to be on the alert for cases of possible. West Nile virus in pregnant women this summer, as investigators attempt to determine the effects of intrauterine exposure.

Congenital infection does occur, but the proportion of infected pregnant women who transmit West Nile virus to their fetuses is unknown and the effects of the virus on the fetus are unclear, Dr. Ned Hayes said at the International Conference on Emerging Infectious Diseases.

The first five cases of congenital West Nile virus infection were seen in 2002. Three of the affected infants, while serologically positive, appeared to be normal, Dr. Hayes said.

One baby was severely infected, having positive IgM and RNA in the cord tissue and placenta. The infant, who died, had cystic cerebral tissue destruction and severe chorioretinitis. The fifth case was a published report of maternal infection, but the infant was not tested (Obstet. Gynecol. 102[2]:229-31. 2003).

The infant who died clearly was infected and had congenital abnormalities, but causality has not been established definitively, Dr. Hayes said.

Flavivirus infection in pregnancy has been associated with spontaneous abortion and neonatal infection, but has not been known to cause birth defects. West Nile virus is a single-stranded RNA flavivirus.

"During 2003 we intensified surveillance, identifying 72 cases of West Nile virus infection in pregnant women," he said. Most occurred in the western and north central states hardest hit that year.

Thus far, 40 of these women have given birth. There has been one neonatal death, an infant with lissencephaly (a malformation involving a lack of convolutions of the cerebral cortex). Two infants had clinical evidence of disease, one with a transient rash and the other with congenital neuroinvasive disease, Dr. Hayes reported at the conference, which was sponsored by the American Society for Microbiology.

One other infant had laboratory evidence of West Nile virus but does not appear to have any abnormalities, Dr. Hayes said.

"We recently published guidelines that we hope will help clinicians evaluate babies who are born with West Nile virus so we can track this and try to figure out what's going on," said Dr. Hayes of the CDC, Fort Collins, Colo.

According to the CDC, pregnant women with signs and symptoms suggesting infection in an area of ongoing West Nile virus infection should be tested and, if serology is positive, the results reported to state or local health departments or to the CDC.

A detailed ultrasound examination is indicated 2-4 weeks after the onset of the maternal viral illness. Amniotic fluid, chorionic villi, or fetal serum can be tested for congenital infection, but the sensitivity, specificity, and predictive value of fetal diagnostic testing are not known (MMWR 53[7]:154-57, 2004).

Clinical evaluation of the neonate should include the following:

* Thorough physical examination, including measurement of head circumference, length, and weight.

* Evaluation for neurologic abnormalities, dysmorphic features, hepatomegaly, splenomegaly, and skin lesions.

* Testing of serum for IgM and IgG antibodies to West Nile virus.

* Evaluation of hearing within 1 month after birth.

* Examination of the placenta by a pathologist if possible. The placenta and a sample of umbilical cord blood also should be retained for further investigation if needed.

The CDC recommends that pregnant women in areas with infected mosquitoes apply insect repellent to skin and clothing and avoid being outdoors during peak mosquito feeding times. Screening of asymptomatic pregnant women is not recommended.

BY NANCY WALSH

New York Bureau

COPYRIGHT 2004 International Medical News Group
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