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West
Nile Virus (WNV) Infection and Breastfeeding: Information for Clinicians
West Nile Virus
(WNV) Infection and Breastfeeding: Information for Clinicians
On
October
4, 2002, CDC's MMWR published a report entitled "Possible
West Nile Virus Transmission to an Infant through Breast-Feeding
- Michigan, 2002." CDC and the Michigan Department of Community
Health continue to investigate West Nile virus (WNV) infection
in a woman and possible transmission to her newborn child. Following
is a summary.
- In
early September 2002, a woman gave birth to a healthy infant.
Post-delivery, the mother required transfusion with 2 units
of packed red blood cells for anemia.
- The
second blood transfusion, given one day after delivery, was
derived from the same donation as a unit given to a liver transplant
recipient who subsequently developed WNV meningitis or encephalitis.
A retained blood specimen from the donation was PCR-positive
for WNV.
- The
mother began breast-feeding her child on the day of delivery.
She was discharged from the hospital 2 days later.
- The
mother developed severe, persistent headache and high fever
(102.8°F) and was readmitted to the hospital 15 days after delivery.
- A
cerebrospinal fluid (CSF) sample was positive for WNV-specific
IgM, and the mother was diagnosed with WNV meningitis or encephalitis.
- A
sample of the mother's breast milk obtained 16 days after delivery
tested positive for WNV-specific IgM.
- The
infant remained afebrile and healthy, although a serum sample
from the infant at age 25 days tested positive for WNV-specific
IgM. Virus culture is pending.
- Neither
WNV nor WNV nucleic acids have been identified previously in
human breast milk.
- Because
the infant had minimal outdoor exposure, it is unlikely WNV
infection was acquired from a mosquito. Therefore, breast milk
must be considered a likely source of infection.
- Currently,
both mother and child are healthy.
Recommendations
for Patients: Because the health benefits of breast-feeding
are well established, and the risk for WNV transmission through
breast-feeding is unknown, these findings do not suggest a change
in breast-feeding recommendations. Lactating women who
are ill or who are having difficulty breastfeeding for any reason,
as always, are advised to consult their physicians.
Following
are questions and answers developed by CDC to assist clinicians
who may receive inquiries from their patients regarding WNV and
breastfeeding.
Q.
Can West Nile virus be transmitted through breast milk?
A. Based on a recent case in Michigan, it appears
that West Nile virus can be transmitted through breast milk. A
new mother in Michigan contracted West Nile virus from a blood
transfusion shortly after giving birth. Laboratory analysis showed
evidence of West Nile virus in her breast milk. She breastfed
her infant, and three weeks later, her baby's blood tested positive
for West Nile virus. Because of the infant's minimal outdoor exposure,
it is unlikely that infection was acquired from a mosquito. The
infant was most likely infected through breast milk. The child
is healthy, and does not have symptoms of West Nile virus.
Q.
Should I continue breast-feeding if I am symptomatic for West
Nile virus?
A. Because the health benefits of breast-feeding
are well established, and the risk for West Nile virus transmission
through breast-feeding is unknown, the new findings do not suggest
a change in breast-feeding recommendations. The American Academy
of Pediatricians and the American Academy of Family Physicians
recommend that infants be breastfed for a full year of life.
Lactating
women who are ill or who are having difficulty breast-feeding
for any reason, as always, should consult their physicians.
Q.
Should I continue breast-feeding if I am not symptomatic for West
Nile virus?
A. Yes. Because the health benefits of breast-feeding
are well established, and the risk for West Nile virus transmission
through breast-feeding is unknown, the new findings do not suggest
a change in breast-feeding recommendations.
Q.
If I am breast-feeding, should I be tested for West Nile virus?
A. No. There is no need to be tested just because
you are breast-feeding.
Q.
Is there any evidence that West Nile virus is transmitted from
mother to child during pregnancy or during birth?
A. There is one documented case of transplacental (mother-to-child)
transmission of WNV in a human. Although the newborn in this case
was infected with WNV at birth and had severe medical problems,
it is unknown whether the WNV infection itself caused these problems
or whether they were coincidental. More research will be needed
to improve our understanding of the relationship - if any - between
WNV infection and adverse birth outcomes.
Nevertheless,
pregnant women should take precautions to reduce their risk for
WNV and other arboviral infections by avoiding mosquitoes, using
protective clothing, and using repellents containing DEET (See
Using Repellent Safely).
When WNV transmission is occurring in an area, pregnant women
who become ill should see their health care provider, and those
whose illness is consistent with acure WNV infection, should undergo
appropriate diagnostic testing.
See
MMWR
Dec 20, 2002 for more information.
Q.
Are infants at higher risk than other groups for illness with
West Nile virus?
A. No. West Nile virus illnesses in children
younger than 1-year-old are infrequent. During 1999-2001, no cases
in children younger than one year of age were reported to CDC.
Of the over 2500 total West Nile Virus cases in 2002, only four
were less than one year of age. We know that one of these infants
was not breast-feeding, and investigation of the other infants
is underway.
Q.
If I am breast-feeding, should I use insect repellent containing
DEET?
A. Yes. Insect repellents help people reduce
their exposure to mosquito bites that may carry potentially serious
viruses such as West Nile virus, and allow them to continue to
play and work outdoors. There are no reported adverse events following
use of repellents containing DEET in pregnant or breast-feeding
women.
For
additional information regarding WNV, please see http://www.cdc.gov/ncidod/dvbid/westnile/
Questions
can be directed to CDC Public Information at 1-888-246-2675 (English),
1-888-246-2857 (Spanish), and 1-866- 874-2646 (TTY).
For
the full published case report, please see Possible
West Nile Virus Transmission to an Infant through Breast-Feeding
- Michigan 2002. MMWR 2002; 51:877-878.
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