The Human Immunodeficiency Virus (HIV) attacks the immune system and is transmitted through certain bodily fluids, including breast milk. Without intervention, the risk of an infant contracting HIV through breastfeeding is estimated to be around 15%, though this rate depends on various factors. Recent medical advancements, particularly Antiretroviral Therapy (ART), have made transmission highly preventable. Understanding the biological process, influencing factors, and public health recommendations is important for minimizing transmission risk.
The Biological Mechanism of Transmission
HIV is present in breast milk in two primary forms: as cell-free viral particles and as virus contained within infected immune cells. The concentration of the virus in breast milk is linked to the amount circulating in the mother’s blood, though it is typically lower. These infected cells and free viral particles are ingested by the infant during feeding.
The transfer of the virus to the infant occurs through the delicate mucosal lining of the gastrointestinal tract. While the exact mechanism is not fully defined, the virus can be absorbed directly through mucosal surfaces or enter through microscopic abrasions or inflammation in the infant’s mouth or gut.
Factors Influencing Transmission Risk
The most important determinant of transmission risk during breastfeeding is the mother’s viral load, which is the amount of HIV detectable in her blood. A higher viral load directly correlates with a higher level of the virus in her breast milk, increasing the likelihood of transmission. Conversely, a low or undetectable viral load significantly reduces this risk.
Local conditions affecting the mother’s breast health also play a role. Conditions like mastitis, breast abscesses, or cracked nipples cause inflammation, which increases the concentration of HIV-infected immune cells within the breast milk. The duration of breastfeeding is another factor, as the risk is cumulative, meaning a longer period of exposure increases the overall chance of infection. Infant factors, such as oral thrush, can create mucosal breaks that may facilitate the virus’s entry into the bloodstream.
Global Recommendations for Infant Feeding
Public health guidance on infant feeding for mothers with HIV varies based on the resources available in a given region. In resource-rich settings, where access to clean water, affordable formula, and reliable healthcare is available, providers historically recommended formula feeding to eliminate transmission risk entirely. However, organizations like the Centers for Disease Control and Prevention (CDC) have updated their guidance to support shared decision-making, acknowledging that the risk of transmission is less than 1% when the mother maintains an undetectable viral load on ART.
In resource-limited settings, the World Health Organization (WHO) prioritizes overall infant survival. Avoiding breastfeeding can significantly increase the risk of infant death from malnutrition, diarrhea, and other infectious diseases due to unsafe formula preparation. Therefore, the WHO recommends that mothers with HIV who are on ART should exclusively breastfeed for the first six months, introduce complementary foods thereafter, and may continue breastfeeding for up to 24 months or longer. This policy requires the mother to adhere to lifelong ART to suppress the viral load.
Strategies to Eliminate Transmission Risk
The primary medical strategy to prevent transmission is the consistent use of maternal Antiretroviral Therapy (ART). ART suppresses viral replication, aiming to achieve an undetectable viral load in the mother’s blood. When the viral load is sustained at undetectable levels, the risk of transmission through breast milk is reduced to less than 1%.
Infants are often given prophylactic ART medication for the duration of the breastfeeding period. This infant prophylaxis provides a layer of protection, preventing the virus from establishing an infection if the child is exposed. Non-medical interventions also exist, such as the pasteurization or flash-heating of expressed breast milk, which can inactivate the virus. Mothers who choose formula feeding must follow strict protocols, including using safe water and correctly sterilizing equipment, to prevent other infectious diseases.