Is monkeypox virus transmissible by breastfeeding?

Abstract

Since early May 2022, more than 92 non-endemic-prone countries have been facing an outbreak of monkeypox virus (MPXV) infections. As of 7 September 2022, approximately 53,000 confirmed or suspected cases have been reported to World Health Organization (WHO) and/or European Centers for Disease Control.1 The virus circulating in non-endemic-prone countries is related to the West African Clade. However, the current outbreak shows some differences in clinical features compared to infections in Central and West Africa endemic-prone areas. Most cases are non-severe with so far, only 18 deaths reported; in contrast, in endemic-prone areas fatality rates are commonly between 3% and 10%. The vast majority of persons affected in this outbreak are male (and mainly men having sex with men), while in endemic prone, MPXV countries women are almost equally affected. There is however concern that many more women of childbearing age will be affected if the extremely high household transmission rates as seen in endemic areas are manifest in the present outbreak. As for many other viral infections, children, pregnant/postpartum women, and immunodeficient individuals from endemic areas are at higher risk of developing severe, sometimes fatal forms of MPXV infection. As observed in smallpox, it is very likely that infants infected with MPXV present frequently with severe or lethal forms of the disease. MPXV belongs to the poxviruses family and the Orthopox genus. Orthopoxviruses include 4 viruses of importance for human health: the variola virus responsible for smallpox, the vaccinia virus, the cowpox virus, and the MPXV. There is a 90% genomic homology between variola virus and MPXV. The four human orthopoxviruses share significant characteristics such as a mucocutaneous tropism, animal-to-human, and human-to-human transmission routes. Known transmission routes involve skin-to-skin, mucosa-to-skin, skin-to-mucosa direct contacts (especially with lesional and paralesional areas) as well as air droplets respiratory transmission from individuals with MPXV lung shedding and transmission from direct contact with contaminated fomites surfaces. Based on the conceptual framework described above and noting that more than two criteria are undocumented, there is insufficient evidence to infer that transmission of MPXV and/or of human orthopoxviruses takes place thought breastfeeding. More research is needed to determine possible routes and risks of mother-to-child transmission of human orthopoxviruses through breast milk and breastfeeding. However, even if the occurrence of breast milk transmission of MPX is unknown, there is a high risk of mother-to-child (or child-to-mother) transmission while breastfeeding, due to direct contact with infectious skin or mucocutaneous lesions, including face-to-face, skin-to-skin, mouth-to-mouth, or mouth-to-skin contact. These considerations support the current WHO recommendations on infant feeding in the context of maternal MPXV infection that include case-by-case assessment of transmission risk and, when there is active maternal MPXV infection, the possibility of isolation of the mother from the infant to prevent transmission of the virus.10 Administration of expressed breast milk from a MPXV-infected woman to the infant may be hazardous because of the risk of contamination by mucocutaneous viral shedding during milk collection. The peer review history for this article is available at https://publons.com/publon/10.1111/pai.13861.