Diseases Transmitted Through Breast Milk: Facts and Myths

Breastfeeding is widely recognized as the healthiest way to nourish a newborn, providing essential nutrients, antibodies, and immune protection. However, many parents worry about whether certain diseases can be transmitted through breast milk. This concern has led to confusion, misinformation, and unnecessary fear surrounding breastfeeding.

Understanding which conditions can be transmitted through breast milk, which ones cannot, and when breastfeeding remains safe is essential for making informed decisions. This article separates scientific facts from common myths and provides clarity for parents.

How Breast Milk Protects Babies

Breast milk is not just food; it is a complex biological substance designed to support infant development. It contains antibodies, immune cells, enzymes, and anti-inflammatory compounds that protect babies from infections and help strengthen their immune systems.

In most cases, breastfeeding reduces the risk of illness rather than increasing it. Many viruses and bacteria that affect mothers do not pass into breast milk, and even when they do, breast milk often contains antibodies that help protect the baby.

Diseases That Can Be Transmitted Through Breast Milk

While breastfeeding is safe in the vast majority of situations, there are a small number of conditions where disease transmission through breast milk is possible.

HIV (Human Immunodeficiency Virus)

HIV is one of the most well-documented infections that can be transmitted through breast milk. Without medical intervention, the risk exists during breastfeeding. However, with proper antiretroviral treatment and medical supervision, the risk can be significantly reduced in many cases.

Healthcare providers carefully evaluate whether breastfeeding is recommended based on the mother’s health, treatment plan, and local medical guidelines.

HTLV-1 and HTLV-2

Human T-cell lymphotropic viruses (HTLV-1 and HTLV-2) can be transmitted through prolonged breastfeeding. In regions where these viruses are common, alternatives to breastfeeding may be recommended.

Active Tuberculosis (Untreated)

Tuberculosis is not transmitted directly through breast milk, but close contact during breastfeeding may expose the baby to airborne infection if the mother has untreated active TB. Once treatment begins, breastfeeding is usually considered safe under medical guidance.

Certain Medications and Substances

Some medications, drugs, and toxic substances can pass into breast milk and may pose health risks to infants. This includes certain chemotherapy drugs, radioactive treatments, and illicit substances. These are not diseases, but they can create unsafe breastfeeding conditions.

Disease	Transmission Fact	Medical Recommendation
HIV/AIDS	Can be transmitted via breast milk.	In the U.S., formula is often recommended. However, if the mother is on stable ART (Antiretroviral Therapy) with an undetectable viral load, the risk is less than 1%.
HTLV-1 & HTLV-2	This rare virus (Human T-cell Lymphotropic Virus) is readily passed through milk.	Breastfeeding is generally not recommended if the mother is positive.
Ebola Virus	The virus has been detected in breast milk during and after infection.	Breastfeeding must be avoided during active or suspected infection.
Brucellosis	An untreated bacterial infection can pass to the infant.	Breastfeeding should be temporarily stopped until the mother has completed treatment.

Diseases That Are NOT Transmitted Through Breast Milk

Many illnesses are incorrectly believed to be transmitted through breast milk. These misconceptions often cause unnecessary stress for new mothers.

Common Viral Infections

Conditions such as colds, flu, COVID-19 (in most cases), and mild viral infections are not transmitted through breast milk. In fact, when a mother is sick, her body produces antibodies that are passed to the baby through breast milk, offering additional protection.

Hepatitis B and Hepatitis C

Hepatitis B and C are not transmitted through breast milk. Babies born to mothers with hepatitis B receive preventive treatment at birth, allowing safe breastfeeding. Hepatitis C also does not pose a breastfeeding risk unless there is active bleeding from cracked nipples.

Mastitis and Breast Infections

Mastitis, a common breastfeeding-related breast infection, does not make breast milk unsafe. Continuing to breastfeed is often recommended, as it helps clear blocked milk ducts and supports recovery.

Common Myths About Breast Milk and Disease Transmission

Myth 1: Any Illness Means You Should Stop Breastfeeding

This is false. Most maternal illnesses do not require stopping breastfeeding. In many cases, continuing to breastfeed actually protects the baby.

Myth 2: Fever Makes Breast Milk Unsafe

Fever does not contaminate breast milk. Breastfeeding during mild illness is generally safe and beneficial.

Myth 3: Antibiotics Always Require Stopping Breastfeeding

Most antibiotics prescribed to breastfeeding mothers are safe. Only a small number require temporary interruption, and this decision should always be guided by a healthcare professional.

Myth 4: Breast Milk Can Easily Become “Infected”

Breast milk is naturally resistant to bacterial growth due to its antimicrobial properties. Proper hygiene and storage further reduce any risk.

When Should Breastfeeding Be Paused?

Temporary or permanent interruption of breastfeeding is recommended only in specific medical situations, such as:

Untreated HIV infection (depending on guidelines)
Certain cancer treatments
Use of illicit drugs
Specific rare viral infections (e.g., HTLV)

In many cases, mothers can pump and discard milk temporarily until breastfeeding can safely resume.

The Importance of Medical Guidance

Every breastfeeding situation is unique. If a mother has a medical condition, is taking medication, or has concerns about disease transmission, consulting a pediatrician or lactation specialist is essential.

Healthcare professionals evaluate risks based on scientific evidence, not myths, ensuring the best outcome for both mother and baby.

Breastfeeding Remains the Safest Choice for Most Babies

Despite widespread misconceptions, breast milk remains one of the safest and most beneficial sources of nutrition for infants. The number of diseases that can truly be transmitted through breast milk is very limited, while the protective benefits are extensive.

By relying on accurate medical information instead of fear-based myths, parents can make confident decisions that support infant health, immunity, and long-term development.

Breastfeeding, when supported with proper guidance and care, continues to be a powerful foundation for a healthy start in life.