Flash-Heating Expressed Breastmilk Emerges as a Low-Tech Safeguard During Infectious Disease Outbreaks

When infectious disease outbreaks strike, one of the most vulnerable points in the chain of infant care is often the feeding decision itself. Concerns that a novel pathogen might pass from mother to child through close contact or through breastmilk have repeatedly led health authorities to recommend temporary cessation of breastfeeding, pushing families toward commercial milk formula and other substitutes. Yet the risks of artificial feeding, including increased rates of diarrheal disease, respiratory infections, and overall infant morbidity and mortality, are well documented and are amplified dramatically in low-resource settings. A new scoping review published in Frontiers in Nutrition suggests that a remarkably simple household technique, known as flash-heating, could offer a way to keep maternal breastmilk in the infant diet even when direct breastfeeding is deemed unsafe.

The review, led by researchers from Johns Hopkins Bloomberg School of Public Health and collaborators across Australia, Canada, South Africa, the United States, and the United Kingdom, followed Joanna Briggs Institute guidelines and the PRISMA-ScR reporting checklist. The team searched PubMed, Scopus, CINAHL, Embase, and Web of Science, supplemented by grey literature from organizations such as the World Health Organization and PATH, along with forward citation searching. From 7,030 records identified, 24 studies published between 2005 and 2025 met the inclusion criteria. Two independent reviewers screened and extracted data using Covidence software, evaluating each study against three domains: microbiological safety, preservation of nutritional and immunological components, and feasibility in low-resource and outbreak settings.

Flash-heating was originally developed more than two decades ago to give HIV-positive mothers in resource-limited settings a way to eliminate the risk of transmitting the virus through breastmilk. The method is deliberately low-technology. Fifty to one hundred twenty milliliters of expressed milk are placed in an uncovered 450-milliliter glass food jar, which is set inside a one-to-two-liter pan containing roughly 450 milliliters of water, with the water level standing two fingers above the milk line. The pan is heated over an electric hot plate or gas stove until the water reaches a rolling boil at 100 degrees Celsius, at which point the jar is immediately removed and rapidly cooled in a cool water bath. The approach is designed to approximate the conditions of high-temperature short-time pasteurization, the industrial standard that holds milk at 72 degrees Celsius for 15 seconds, but using only common household equipment.

The microbiological evidence assembled in the review is encouraging. Field and clinical studies demonstrated that flash-heating substantially reduces common bacterial contaminants of breastmilk, including Escherichia coli, Staphylococcus aureus, and Group B Streptococcus, organisms frequently introduced through handling or maternal mastitis. Although Staphylococcus aureus is relatively heat-tolerant, significant reductions in bacterial load were observed, though complete growth inhibition was not consistently achieved. On the viral side, flash-heating reduced HIV viral load in breastmilk, affecting both cell-free and cell-associated virus, a finding consistent with the known heat sensitivity of lipid-enveloped viruses. Laboratory studies of high-temperature short-time treatment, used as contextual evidence, indicate that most vegetative bacteria and enveloped viruses are readily inhibited at temperatures around 72 degrees Celsius, whereas non-enveloped viruses such as porcine parvovirus show marked heat resistance, suggesting that similar pathogens may be less susceptible to brief heat exposure.

Notably, the review uncovered a significant methodological gap: in half of the studies investigating flash-heating and pathogen inactivation, the temperature of the breastmilk itself was never directly measured. Instead, researchers assumed the milk had reached 72 degrees Celsius for 15 seconds based on the protocol. Temperatures achieved varied between studies, and contextual factors such as altitude and heating rates may influence the actual temperatures reached, potentially affecting pathogen inactivation. This variability complicates comparisons across the evidence base and underscores the need for standardized protocols with direct temperature monitoring.

On the nutritional side, the picture is largely reassuring. Flash-heating had no negative impact on total carbohydrates and fat content, and micronutrients including vitamins A, B1, B6, B12, and E were well preserved with little to no loss. Vitamin B2 retention ranged from 59 to 100 percent, vitamin C from 39 to 100 percent, and folate from 76 to 100 percent, depending on the specific procedure used. Total oligosaccharides, the largest sugar component of human milk and a critical fuel for the infant gut microbiome, were completely preserved. The one clear casualty was lipase activity, the enzyme important for fat digestion in infants, which was almost completely destroyed by heat treatment, as expected.

Immunological components fared less uniformly. Immunoglobulins IgA and IgG were preserved to a moderate degree, with retention ranging from 25 to 80 percent depending on peak temperature and the volume of milk heated. Cytokines IL-8 and IL-10 were well preserved, with retention approaching 100 percent. In contrast, lactoferrin concentrations dropped to between 16 and 30 percent of original levels, and lysozyme concentrations fell to between 21 and 60 percent. Interestingly, the bactericidal activity of both lactoferrin and lysozyme was relatively better preserved than their concentrations, with lactoferrin activity retention ranging from roughly 39 to 89 percent and lysozyme activity from 43 to 78 percent. Compared with high-temperature short-time pasteurization, flash-heating resulted in greater reduction of immune components overall, though at least one-third of most immunological factors remained intact.

The feasibility data, drawn almost entirely from the HIV context, offer a glimpse of how the technique performs in real households. In Tanzania, 51.4 percent of HIV-infected mothers who received home-based infant feeding counseling initiated flash-heating over a six-month period, practicing it for an average of 9.6 weeks regardless of age, religion, parity, or education. In rural Zimbabwe, 20 HIV-infected mothers adopted the method for a mean duration of 4.5 months with nurse support, achieving peak milk temperatures of 79.3 to 80.5 degrees Celsius. The technique was implemented using readily available household materials, including glass jars, aluminum pans, cups, and common fuels such as kerosene and charcoal, with heated water often reused for cooking or bathing. Reported barriers included difficulties with expressing breastmilk, fuel shortages, conflicting guidance from health workers, and limited familiarity with heating practices, while facilitators included peer counselor support, household backing from husbands, low-cost materials, and perceived benefits for infant health.

The authors emphasize that the choice in an outbreak is not between flash-heating and a risk-free alternative, but between flash-heating and the known, well-documented risks of commercial milk formula and other substitutes in low-resource settings. Breastmilk retains a wide range of bioactive components even after heat treatment that are absent from artificial substitutes, including hundreds of oligosaccharides and prebiotic sugars that support commensal gut bacteria, inhibit pathogen adhesion, and modulate immune responses. Formula feeding, by contrast, makes infants susceptible to pathogen colonization through disruption of the intestinal mucosa. Global guidance from the World Health Organization and the Operational Guidance on Infant and Young Child Feeding in Emergencies already prioritizes mother’s own expressed milk and donor human milk before commercial substitutes, yet gaps remain in operationalizing these frameworks when breastfeeding is interrupted by outbreaks.

Looking forward, the review calls for research on a broader range of outbreak-relevant pathogens, including Ebola virus, cytomegalovirus, and Zika virus, along with standardized protocols defining heating duration, target temperature, and acceptable variability. Simple, low-cost tools such as thermometers placed directly in the milk, or calibrated devices like the FoneAstra and PiAstra monitors already shown to be effective, could support consistent application. Future work must also examine the full operational pathway, from safe expression and heating through post-heating handling and storage, with particular attention to the risk of recontamination after treatment. Long-term safety, clinical outcomes, infant growth, and effects on the gut microbiota remain unexplored. Strengthening this evidence base, the authors conclude, will be essential to support clear, context-sensitive public health recommendations that keep human milk at the center of infant feeding, even in the most challenging outbreak conditions.

Subject of Research: Flash-heating of expressed breastmilk as a low-cost pasteurization method for pathogen inactivation and nutrient preservation during infectious disease outbreaks

Article Title: A scoping review of microbiological safety, bioactive components, nutrient retention, and feasibility of flash-heating expressed breastmilk: exploring potential use during infectious disease outbreaks

Article References: A scoping review of microbiological safety, bioactive components, nutrient retention, and feasibility of flash-heating expressed breastmilk: exploring potential use during infectious disease outbreaks. (n.d.). https://doi.org/10.3389/fnut.2026.1926806

Image Credits: AI Generated

DOI: 10.3389/fnut.2026.1926806

Keywords: flash-heating, breastmilk, pasteurization, infectious disease outbreaks, pathogen inactivation, immunoglobulins, human milk oligosaccharides, HIV, infant feeding, low-resource settings, emergency nutrition, scoping review