Officials suspect virus caused brain defects in New York infant

By Jim Erickson, Rocky Mountain News
December 20, 2002

A New York infant born with severe brain defects contracted West Nile virus in the womb and health officials suspect the germ caused her abnormalities.

The month-old Syracuse infant is the first documented victim of intrauterine West Nile virus transmission, federal health officials announced Thursday.

"It's very possible that West Nile virus was the cause of the baby's neurological deficits, but with only one case, it's impossible to really determine cause and effect," said Dr. Lyle Petersen, deputy director of the Centers for Disease Control and Prevention laboratory in Fort Collins.

Though transmission of West Nile in the womb is probably rare, CDC officials urged pregnant women to avoid mosquitoes by wearing protective clothing and using repellents that contain DEET.

Pregnant women who live in areas where West Nile is active should seek medical care if they develop an illness with fever. If their doctor thinks it's appropriate, they should be tested for West Nile infection, said Dan O'Leary, a medical epidemiologist at CDC's Fort Collins lab.

That lab heads CDC's national response to West Nile, which sickened more than 3,800 Americans this year, killing 232 of them. Colorado had 12 non-fatal West Nile cases.

For every person who becomes seriously ill from West Nile, at least 150 others are bitten by infected mosquitoes but don't get sick, CDC officials estimate.

"With the hundreds of thousands of people infected this year, many pregnant women were undoubtedly exposed to the virus," Petersen said Thursday during a news briefing.

"The fact that we haven't seen a great deal of suspect cases is fairly reassuring," he said.

West Nile is normally transmitted by mosquitoes, but the insidious microbe continues to surprise researchers with its ability to invade the human body by other routes.

The first cases of West Nile transmission through organ transplant were reported this year. And at least 13 Americans contracted the virus through blood transfusions in 2002, prompting blood banks across the nation to quarantine about 30,000 pints of plasma.

One infant may have acquired West Nile through breast milk. Even sexual intercourse "could potentially be a mode of transmission," though there is no hard evidence to support the idea, Petersen said.

In the Syracuse case, a previously healthy 20-year-old woman tested positive for West Nile in mid-October and gave birth to a full-term baby girl five weeks later.

The infant's birth weight and outward appearance were normal, but an eye exam revealed inflammation of the retinas in both eyes.

That led to an MRI of the infant's head, which showed extensive loss of brain cells at the back of the brain and on both sides.

"The infant has had destruction of part of its brain, for whatever cause," Petersen said Thursday.

"And whenever you have this degree of destruction of the brain cells, it would be expected that there would be some cognitive and other neurological abnormalities associated with that," he said.

The baby girl, whose blood contained antibodies to West Nile virus, is being evaluated for possible complications from the infection, said Dr. Lloyd Novick of the Onondaga County Health Department in New York.

The mother is "continuing to recover" at home, Novick said.

Health officials have ruled out other viruses as the cause of the infant's brain defects, O'Leary said. And the mother's medical history didn't reveal any risk factors that might explain them.

This year, CDC tracked one other case of a woman who became infected with West Nile during pregnancy, then gave birth. That baby was born healthy and West Nile-free, O'Leary said.

"Our sense is that this is an uncommon occurrence," he said. "But this is the first such case that has ever been reported, so we need to follow it closely over time."

Also during Thursday's news briefing, CDC officials said more than 2,300 cases of West Nile encephalitis and meningitis were reported in the United States this year. That makes the 2002 outbreak the largest epidemic of West Nile-caused encephalitis and meningitis ever documented, O'Leary said.

ericksonj@RockyMountainNews.com or (303) 892-5129