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Baby Catches West Nile Virus by Breast-Feeding

Mother sickened by transfusion, but officials say newborn is OK

THURSDAY, Oct. 3, 2002 (HealthDayNews) -- Health officials today confirmed that a Michigan newborn appears to have contracted the West Nile virus through its mother's breast milk, becoming the youngest person on record with the infection.

The child, whose gender has not been released, has no fever and appears to be doing well, according to the U.S. Centers for Disease Control and Prevention, which is investigating the case. The infant's mother, who did develop symptoms of West Nile, is believed to have been infected last month by a blood transfusion during delivery. Another Michigan resident contracted the disease after receiving a transfusion from the same donor.

Genetic traces of West Nile turned up in the woman's breast milk late last month, prompting officials to test the baby's blood for evidence of the virus. The woman, a 40-year-old, first-time mother, nursed the baby for more than two weeks before she was diagnosed with the disease.

Tests found IgM proteins, or antibodies, specific to West Nile that almost certainly indicate infection through nursing, said Dr. Lyle Petersen, a CDC West Nile expert. "The overwhelming evidence is that the child was actually infected with the West Nile virus," Petersen said at a news teleconference.

"Because of the infant's minimal outdoor exposure, it is unlikely that infection was acquired from a mosquito," the CDC writes in tomorrow's publication Morbidity and Mortality Weekly Report. "Therefore, breast milk must be considered as the most likely source."

State and federal infection experts are still studying the mother's milk to see if it contains live particles of the pathogen, rather than simply shards of its genes. The results of those tests are pending, officials said.

Four other infants this year fell ill with West Nile fever, Petersen said, though it's not known whether three of them breast-fed. The fourth did not nurse, Petersen said. Between 1999 and 2001, the CDC did not receive a single report of a baby under age 1 with the disease.

Both Petersen and Dr. Matthew Boulton, Michigan's state epidemiologist, said the risk of passing West Nile through nursing was slight and didn't warrant abandoning breast-feeding. "We would continue to recommend that women breast-feed, given the well-documented benefits of doing so," Boulton said.

Last week, officials advised nursing women with confirmed cases of West Nile to talk with their doctor about whether to stop breast-feeding.

This year's West Nile infection tally reached 2,530 cases yesterday, including 116 deaths. While the average age of people with the disease is 56, the average age of those killed by it is 79, reflecting the fact that the virus preys especially on the elderly and infirm.

Mosquito bites caused the vast majority of this year's infections. However, health officials said 15 people in 10 states developed West Nile brain inflammation after receiving donated blood or blood products contaminated with the microbe. Petersen said transfusions were to blame for at least three cases, but it's possible that mosquitoes may have caused some of the others.

"Other than blood [and breast milk], we do not have any evidence that West Nile virus is transmitted by any other body fluid," said Petersen, who acknowledged the agency has not looked at other fluids so far and has no plans to do so.

The U.S. Food and Drug Administration is now debating whether to screen the nation's blood supply for West Nile virus. While the risk of catching the infection through a transfusion is small, Petersen said people scheduled for elective surgery may want to delay the procedure until the disease season ends in few weeks.

"The West Nile virus season is waning," Petersen said. "Blood that is collected is likely to be safer and safer."

What To Do

For more on West Nile virus, try the CDC, the U.S. Food and Drug Administration or the Maryland Department of Health and Mental Hygiene.

SOURCES: Lyle Petersen, M.D., M.P.H., medical epidemiologist, U.S. Centers for Disease Control and Prevention, Atlanta; Matthew Boulton, M.D., Michigan state epidemiologist; Oct. 4, 2002, Morbidity and Mortality Weekly Report
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