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Signs of West Nile virus found in breast milk of new mother
By Lauran Neergaard, Associated Press, 09/27/02
WASHINGTON — Scientists have found genetic signs of West Nile virus in the breast milk of a new mother battling the infection, the latest surprise as the virus continues to spread throughout the country.
The Michigan woman's 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."
The 40-year-old Michigan mother gave birth on Sept. 2, and received a blood transfusion that day and the next. She went 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, a liver transplant recipient, received blood from a common donor, and remaining blood samples from that donor show signs of contamination.
West Nile virus is mostly spread through mosquito bites, and has infected 2,206 people in 32 states so far this year and killed 108, the CDC said. But the government discovered this month that West Nile virus apparently can be spread through blood transfusions, as well as organ transplants, although it considers the risk low.
Now the question is whether it can be spread through breast milk.
The Michigan 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 if 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, who was not identified, will decide whether to resume breast-feeding after test results are back.
There have never been signs, here or in other countries where West Nile is rampant, that West Nile virus could be spread through breast-feeding. Currently, doctors recommend against breast-feeding only for mothers who have the AIDS virus or another infection called HTLV-1.
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 spread orally, too.
But only four of this year's infections have been in babies younger than 1 year, the typical age of breast-feeding. "This would suggest the risk of West Nile virus infection to breast milk is going to be low, if there is any risk at all," Petersen said.
If West Nile does enter breast milk, it wouldn't linger there long, he added, because people who aren't seriously infected clear the virus out of their bodies quickly.
Most people bitten by an infected mosquito never get sick; the 20 percent who do mostly have mild flu-like symptoms. One in 150 to 200 people, mostly the elderly, get seriously ill.
The CDC had some good news: Although infections are continuing, the West Nile outbreak appears to be winding down as the weather cools. Also, tropical storm Isidore likely washed away mosquito eggs and larvae when it flooded parts of Louisiana and Mississippi this week, possibly providing some short-term relief there before mosquitoes breed again.