WASHINGTON -- Scientists have found genetic signs of West Nile virus in the breast milk of a new mother battling the infection.
Her baby is healthy and there's no evidence yet that West Nile virus actually could be transmitted by breast-feeding, federal health officials stressed Friday -- but they are investigating that possibility.
Breast milk is considered the healthiest food for babies and federal scientists stressed that mothers should not quit nursing because of fear about this year's West Nile outbreak.
But a new mother who has a confirmed diagnosis of West Nile virus should discuss with her doctor whether to continue breast-feeding or quit at least temporarily, said Dr. Lyle Petersen of the Centers for Disease Control and Prevention.
"If she has severe disease and cannot breast-feed easily and provide sufficient nutrition to her child, we certainly in that case recommend supplemental feeding," he said. "On the other hand, breast-feeding has many beneficial effects ... and the decision to discontinue breast-feeding is a big one."
Gave birth Sept. 2
The 40-year-old Michigan mother gave birth on Sept. 2, and received a blood transfusion that day and the next. She had a fever before being sent home with her new baby on Sept. 4 -- only to be rehospitalized on Sept. 17 for three days while suffering what doctors have now confirmed was West Nile virus.
It's not clear how she became infected but it may have been from the blood, the CDC said. She and another patient received blood from a common donor, and remaining blood samples from that donor show signs of contamination.
The government discovered this month that West Nile virus apparently can be spread through blood transfusions but considers the risk low.
The mother has recovered and her infant never was sick.
She breast-fed her baby for two weeks, but her personal physician advised quitting when she was hospitalized. A sample of her breast milk shows traces of West Nile genetic material, the CDC announced Friday -- but that's not proof the baby was actually exposed to the virus, Petersen said.
Doctors took a sample of the baby's blood Friday to check for antibodies to West Nile virus that would show whether the infant was exposed after birth, said Michigan state epidemiologist Dr. Matthew Boulton. Results are due next week.
The CDC also is testing breast milk the mother continued to pump for the presence of actual virus.
Boulton said the woman will decide whether to resume breast-feeding after test results are back.
West Nile virus is predominantly spread by mosquito bites, and many blood-borne infections cannot be spread orally because they don't survive the stomach's acidity. But a tick-borne encephalitis that is a cousin to West Nile can be spread through the milk of infected cows or goats, Petersen said, so it's theoretically possible that West Nile could be, too.