Why is Breast-feeding a risk factor for HIV-1 transmission despite HIV-1 infected mothers receiving combination ART (cART)?

Mother-to-child transmission (MTCT) of human immunodeficiency virus type 1 (HIV-1) is an important source of HIV-1 infection in infants, and can occur at any point, including in utero, at the time of delivery, and via breastfeeding. In the absence of intervention, such as the use of antiretroviral therapy (ART), MTCT of HIV-1 during pregnancy or delivery can affect approximately 15–25% of infants, with a further 5–20% of infants becoming infected postnatally during breastfeeding. The use of maternal ART while breastfeeding reduces the MTCT risk from 35% without any intervention to less than 5%. Although a significant improvement, 5% of infants continue to be infected.i Maternal factors that contribute to this continued risk of transmission despite taking ART include the method of feeding, breast health, RNA and DNA viral load in breast milk and plasma, and maternal nutrition. Infantfactors such as the disruption in the integrity of the gastrointestinal mucosal surfaces also contribute to an increased rate of MTCT.Aims: This literature review aimed to investigate why breastfeeding is still a risk factor despite HIV-1-infected mothers being on effective combination ART (cART)? This review will explore the associated factors that contribute to the increased risk of HIV-1 transmission to the infant via breastfeeding