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Breastfeeding and West Nile Virus
By Kelly Bonyata, IBCLC
(This is current info as of September 2006)
Breastfeeding mothers have been concerned about West Nile Virus
(WNV) since the flurry of publicity in Fall 2002 about the transmission
of West Nile via breastmilk.
The current
recommendation from the US Centers for Disease Control is that
a mother should not interrupt breastfeeding
if she contracts West Nile Virus, since the risk to the baby
from weaning to infant formula is greater than the risk posed by
the potential WNV infection.
Here is what we know:
- Components of breastmilk (IgG, IgM, lipids) have been shown
in laboratory tests (in vitro) to be active against West Nile
Virus. See Antiviral
factors found in human milk for more information.
- Live West Nile Virus (the intact, infectious form of the virus)
has not been cultured from breastmilk. Fragments of genetic material
(RNA) and WNV-specific antibodies have been cultured from breastmilk.
- In September 2002, a woman contracted West Nile Virus from a
postpartum blood transfusion. Her newborn was exclusively breastfed
and exposure to WNV through anything other than breastmilk was
unlikely.
- At 16 days postpartum, the mother's breastmilk tested positive
for WNV antibodies (IgM, IgG) and WNV genetic material (RNA,
not the live virus).
- At 17 days postpartum, the mother discontinued breastfeeding.
- At 24 days postpartum, the mother's milk tested negative for
WNV genetic material (RNA), and positive for WNV antibodies
(IgM).
- At 25 days postpartum, the infant's blood plasma tested positive
for WNV antibodies (IgM).
- Per the CDC:
"Although WNV genetic material was
present transiently in breast milk, the specific timing and
source of the infant's infection remain unclear... Until live
virus is cultured from breast milk, or until definitive data
are obtained to document WNV transmission through breast milk,
the findings described in this report should be interpreted
with caution."
- source: CDC. Possible
West Nile Virus Transmission to an Infant Through Breast-Feeding
--- Michigan, 2002. MMWR 2002;51(39);877-878.
- Per the CDC:
"WNV RNA has not been identified
previously in breast milk, and no studies are known that define
the implications of this laboratory finding. Laboratory investigations,
including attempts to culture WNV from additional breast milk
samples, are under way. Until live virus is cultured from breast
milk, or until definitive data are obtained to document WNV
transmission through breast milk, the TaqMan® findings described
in this report should be interpreted with caution... The risk
for transmission of WNV from mother to infant through breast-feeding
is unknown. The infant described in this report remains healthy
despite breast-feeding for 17 days. Until follow-up testing
on the infant is completed, it is unknown whether the infant
was infected with WNV. The health benefits of breast-feeding
are well established, and these findings do not suggest a change
in breast-feeding recommendations."
- source: CDC. Update.
Investigation of West Nile Virus Infections in recipients of
Organ Transplantation and Blood Transfusion---Michigan, 2002.
MMWR 2002;51:879.
- The baby remained healthy throughout
and had no symptoms of West Nile Virus.
Keep in mind that in many cases where mom has been exposed to West
Nile Virus via mosquito bites (the primary route of infection),
baby has also been in contact with those same mosquitos.
If mom does become infected with WNV, she will likely not know
about it until symptoms appear (3-14 days), and baby will have already
been exposed to the virus at that point (via a mosquito bite and/or
breastmilk). Breastfeeding builds baby's immune system and will
also provide baby with extra antibodies to West Nile Virus.
Discontinuing breastfeeding would deprive baby of the extra immune
protection from breastfeeding, and is not advised.
Page last modified:
03/03/2005
Written: 6/13/03
Additional Information on West Nile Virus & Breastfeeding
West
Nile Virus and Breast-feeding FAQ from the US Centers for Disease
Control
More from the CDC:
West
Nile Virus: Pregnancy & Breastfeeding from Health Canada
Breastfeeding
and the West Nile Virus by Kimberly G Lee, MD, MS
Centers
for Disease Control give OK for continued breastfeeding in mothers
with West Nile Virus La Leche League International Press Release
General information - Articles
General information - Websites
