The impact of thermal pasteurization on viral load and detectable live viruses in human milk and other matrices: a rapid review

Abstract

<jats:p> Holder pasteurization (62.5ºC, 30 min) of human milk (HM) is thought to reduce the risk of transmitting viruses to an infant. Some viruses may be secreted into milk – others may be contaminants. The effect of thermal pasteurization on viruses in HM has yet to be rigorously reviewed. The objective of this study is to characterize the effect of common pasteurization techniques on viruses in HM and non-HM matrices. Databases (MEDLINE, Embase, Web of Science) were searched from inception to April 20th, 2020 for primary research articles assessing the impact of pasteurization on viral load or detection of live virus. Reviews were excluded, as were studies lacking quantitative measurements or those assessing pasteurization as a component of a larger process. Overall, of 65,131 reports identified, 109 studies were included. Pasteurization of HM at a minimum temperature of 56ºC-60ºC is effective at reducing detectable live virus. In cell culture media or plasma, coronaviruses (e.g., SARS-CoV, SARS-CoV-2, MERS-CoV) are highly susceptible to heating at ≥56ºC. Although pasteurization parameters and matrices reported vary, all viruses studied, except parvoviruses, were susceptible to thermal killing. Future research important for the study of novel viruses should standardize pasteurization protocols and should test inactivation in human milk.&#x0D; Novelty bullets&#x0D; •In all matrices, including human milk, pasteurization at 62.5ºC was generally sufficient to reduce surviving viral load by several logs or to below the limit of detection.&#x0D; •Holder pasteurization (62.5ºC, 30 min) of human milk should be sufficient to inactivate non-heat resistant viruses, including coronaviruses, if present&#x0D; </jats:p>

Universal Screening for SARS-CoV-2 of all Human Milk Bank Samples

“…However, our observations, combined with the negativity of human milk samples after Holder pasteurization confirmed by different authors (Pitino et al, 2020;Unger et al, 2020;Walker et al, 2020), support that donor human milk is a safe product, after carrying out an appropriate evaluation of donor mothers to obtain eligibility for the donation. To the best of our knowledge, our study is the first one to analyze human milk containers and milk samples from all donor mothers.…”

“…Cold storage of SARS-COV-2 in human milk did not significantly change viral load over a 48 hr period according to a study in which the virus was experimentally inoculated into human milk samples (Walker et al, 2020). Nevertheless, SARS-CoV-2 is effectively inactivated by Holder pasteurization (62.5°C, 30 min) of human milk, if present (Pitino et al, 2020;Unger et al, 2020). These observations suggest that current human milk bank (HMB) processes would effectively reduce an eventual risk of transmission of respiratory viruses such as SARS-CoV-2 to most fragile neonates.…”

Analysis of Thermal Sensitivity of Human Cytomegalovirus Assayed in the Conventional Conditions of a Human Milk Bank

“…In conclusion, our data clearly confirm that the heat treatment for 30 min at 60°C guarantees the total inactivation of HCMV. Taking into account that previous reports suggest that this is also applicable to other breastfeeding transmitted viruses, like HIV, HTLV and Parvovirus B19 ( 16 , 17 ), we consider that this variant of Holder pasteurization may be a good compromise between the microbial inactivation and the preservation of nutritional properties using the same pasteurizer equipment found in most of Human Milk Banks. These aspects make the procedure of pasteurization favorable especially in low-income countries.…”

“…Therefore, the aim of this work has been to evaluate the temperature sensitivity of HCMV during the processing of donor breast milk under the same conditions that are commonly used in human milk banks. If it is confirmed that HCMV is destroyed at temperatures lower than that used in Holder pasteurization, as shown in the literature for most infectious agents ( 16 , 17 ), the possibility of a thermal treatment of donated milk more respectful with its biological components would be possible and this would be beneficial for the receptors.…”

“…There are clear evidences that temperatures lower than those recommended nowadays (Holder pasteurization; 30 min at 62.5 • C) are less deleterious with the biological components of milk, whereas, retaining the capacity to destroy bacterial and viral [HIV, HTLV-I, Polioviruses, Chikungunya Virus (CHIKV), West Nile Virus (WNV)] contaminations in donor human milk (16,17). Unfortunately, there are few data about the sensitivity of Human Cytomegalovirus (HCMV) to the range of temperatures between 56 and 63 • C. In a recent paper (18) Maschmann et al, concluded that temperatures above 60 • C for performing short-term pasteurization are enough for the purpose of CMV inactivation.…”