HIV viral load in breast milk: no easy predictors in South African study30 January 2003,
Julian Meldrum, AIDSmap.com,

"A simple formula for predicting which mothers may be at highest risk of transmitting HIV through breastfeeding may not be available, according to a South
African study reported in the February 14th edition of AIDS.

The study set out to explore factors related to HIV viral load in breast milk and the risk of transmission from mothers to babies. It also tried to explain why babies that are exclusively breast-fed appear less likely to become HIV positive than babies fed with breastmilk and other food and drink (including water).

The study was carried out in Durban between 1997 and 1999, and recruited 145 breast-feeding HIV positive women. At several time-points after birth (1, 6 and 14 weeks) women expressed milk from each of their breasts which was then tested for HIV and indicators of low-level inflammation (mastitis) which is suspected of boosting HIV viral load in milk....

While the study confirmed that there is a highly significant correlation between mastitis, as shown by the sodium/potassium ratio in the milk exceeding 1.0, it also found that this explained only a small part of the variation in viral load which was found in the different breastmilk samples.
... According to this research, treatments (to deal promptly with infections) and other measures (such as nutritional supplements and education on how best to breast-feed babies) to prevent low-level mastitis might be expected to prevent as few as 5% of cases of HIV transmission to babies. Nonetheless, because these measures are of low cost and can benefit mothers and infants regardless of HIV status, the case for implementing them is strong.

The need for further research, including studies to look at the impact of ARV treatment of breastfeeding women on the levels of HIV in their milk, is clear.

[Can't argue with that conclusion... - JC]