Research published in the Lancet has highlighted a lower risk of HIV transmission with exclusive breastfeeding by HIV positive mothers (4% risk), compared to mixed feeding (10-40% risk). Research on the timing of HIV transmission in 2000 revealed that a "substantial transmission occurs early during breastfeeding," concluding that 75% of all breast milk transmission had occurred within the first 6 months during a randomized control trial in Kenya. This research is of particular importance in developing countries where infant formula is not widely available or safe to prepare. In fact, the World Health Organization recommended breastfeeding in 1987 and 1992 for seropositive and seronegative women in areas where malnutrition and infectious diseases are the major cause of infant mortality. In 1996 UNAIDS issued a recommendation that women in developing countries consider the risks and benefits of each feeding practice on an individual level; they recommended women make an informed choice about infant feeding. In the days before the AIDS epidemic was clearly understood, some researchers pointed to the need to increase breastfeeding rates and pointed to the risks of formula feeding, citing increased rates of marasmus and diarrhea. D Jelliffe and E Jelliffe also criticized the marketing of infant formulas by US companies to resource-poor countries, something they termed "comerciogenic malnutrition." A more recent article from 1992 describes how the health of an infant can be compromised by water, which in many resource-poor countries holds the risk of environmental pathogens that are not present in breastmilk.