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Pregnant Woman Passes West Nile to Baby

Infant has defects in first known mother-to-child transmission

THURSDAY, Dec. 19, 2002 (HealthDayNews) -- In what's believed to be a first, health officials suspect a pregnant woman in upstate New York passed the West Nile virus on to her unborn baby last summer, apparently leading to "extensive" birth defects.

Officials had previously seen one case of West Nile in a pregnant woman, but her baby was unaffected by the virus. However, a range of microbes, including relatives of West Nile, can pass from mother to fetus and cause potentially serious damage.

"It's not particularly surprising that eventually we would discover a case of intrauterine infection in a West Nile-infected mother," said Dr. Daniel O'Leary, a West Nile expert at the U.S. Centers for Disease Control and Prevention.

He said the agency isn't certain the New York newborn's birth defects resulted from West Nile infection. But no other explanation fits better.

The 20-year-old mother was hospitalized in late August with fever, headache, blurred vision, vomiting, and back and abdominal pain. At that time, she was treated with antibiotics and underwent a series of neurological tests.

She left the hospital on Sept. 14 against her doctors' advice, but returned two days later. Subsequent blood tests proved positive for West Nile infection. The woman gave birth in mid-November, carrying the baby to term. (CDC officials declined to identify the newborn's gender, but the Post-Standard of Syracuse said it was a girl.) Blood samples from the baby were positive for antibodies to the virus that can only reflect an active infection, officials said.

Doctors identified eye problems with the infant in a physical exam once it was known that the baby had signs of infection, O'Leary said. Subsequent brain imaging tests turned up "extensive pathologic changes," said O'Leary, who would not elaborate on the baby's condition.

Dr. Lyle Petersen, another CDC West Nile specialist, called the prospect of intrauterine transmission of West Nile "very possible." But "with only one case it's impossible to really determine cause and effect," he said.

Even so, the West Nile's map of transmission now includes an impressive array of routes, from mosquito bites to blood donations and tissue grafts. Earlier this year, officials identified a likely case of West Nile infection passed through breast milk from a Michigan mother to her nursing infant.

The CDC has also learned of two cases of West Nile infection in lab workers handling afflicted animals. In each incident, microbiologists contracted the virus after accidental skin breaks with contaminated instruments.

This year saw a worrisome increase in West Nile infections. The number of cases ballooned from 149 between 1999 and 2001 to nearly 3,400 by Nov. 30 2002, officials said. Initially limited to the East Coast, infections appeared across the country, showing up in 2,289 counties in 44 states and Washington, D.C., health officials said.

Nearly 70 percent of the cases involved meningoencephalitis, or inflammation of the brain and spinal cord. The remaining patients developed West Nile fever, a milder form of illness.

Of the ill, 201 died, 199 of whom had brain and spinal cord infections. Older people are much more likely than younger patients to suffer the more serious form of West Nile infection, and their risk of death is higher, too.

Petersen said "hundreds of thousands" of people may have been infected with West Nile virus this year but didn't develop symptoms of the disease or never sought treatment. Six states in the Midwest and South -- Illinois, Indiana, Louisiana, Michigan, Ohio, and Texas -- were home to most of the confirmed cases, officials said.

Animals were also more vulnerable to the virus this year than ever before. More than 14,000 birds died from West Nile infection, and more than 9,000 horses contracted the disease, 12 times last year's figure, O'Leary said.

Health officials advise pregnant women with fever, headache, and other signs of West Nile infection to ask their doctor about being tested for the virus, which has no treatment. However, they discourage women without symptoms from seeking screening. All pregnant women should try to avoid mosquitoes by wearing protective clothing and using insect repellents that contain DEET.

Health officials have encouraged people in West Nile-infested areas to consider postponing elective surgeries until the mosquito season ends, as it has in most of the country. Still, "the blood supply has never been massively contaminated, " Petersen said. "If you need blood products, West Nile virus should be very low on your list of concerns."

What To Do

To find out more about West Nile, try the Centers for Disease Control and Prevention or the U.S. Geological Survey.

SOURCES: News teleconference with Lyle Petersen, M.D., deputy director for science, division of vector borne infectious diseases, and Daniel O'Leary, D.V.M., medical epidemiologist, Fort Collins, Colo., both with U.S. Centers for Disease Control and Prevention; Dec. 20, 2002, Morbidity and Mortality Weekly Report; Dec. 19, 2002, Syracuse Post-Standard
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