West Nile via breastfeeding seen to be rare

NEW YORK, Mar 13 (Reuters) Although it's a possibility, actual cases of nursing mothers passing on the West Nile virus to their babies through breast milk are very rare, according to the Centers for Disease Control and Prevention.

''West Nile virus has become a major public health threat in the United States,'' Dr. Alison F. Hinckley and colleagues from the CDC in Fort Collins, Colorado, write in the medical journal Pediatrics. The virus, carried by mosquitoes, has caused more than 8000 cases of human disease in the US since it was first detected in New York in 1999.

''In September 2002, the first case of possible West Nile virus transmission via human milk was reported,'' the team notes.

Since 2003, the CDC has collected data on West Nile virus illness in mothers and infants during the breastfeeding period.

''Six infants were reported to have breastfed from mothers with West Nile virus fever,'' Hinckley's group reports. Of these, five infants had no symptoms and no sign of the virus when they were tested. One infant, who was not tested, developed a rash, but appeared well one week after the mother became ill.

In other instances, two infants became infected with West Nile virus during breastfeeding, but no preceding illness in the mothers was documented.

The researchers also found that two breastfed infants whose mothers developed West Nile virus fever during the last week of pregnancy tested positive for the virus. These babies could have acquired the virus in the womb rather than through breastfeeding, Hinckley's group suggests.

The CDC workers also collected 45 milk samples from women infected with West Nile virus during pregnancy, and found signs of the virus in the samples in three cases.

Although transmission of West Nile virus through breast milk appears to be uncommon, more data are needed to understand the potential for transmission, Hinckley's team concludes.

They also suggest that ''for areas where West Nile virus is endemic,'' doctors should include infection with the virus as a possibility when they encounter illness among breastfeeding children and nursing mothers.

REUTERS RL BST1013