Viral Transmission

by Dr Louise Santhanam, General Practitioner

*** Information about Infant Feeding and COVID-19 ***

During simple, common viral illness breastmilk feeding does not need to be interrupted, unless the mother is too unwell to continue (see the NHS Website).  Amongst its many components breastmilk contains immunoglobulins including secretory IgA and oligosaccharides (protective to the GI tract), white blood cells produced in response to maternal infections, viral fragments which can trigger the infant immune system and anti-inflammatory molecules. The maternal entero-mammary and broncho-mammary immune pathways also deliver antibodies to common maternal viral infections via breastmilk to the infant1.

The following information covers the current understanding of the risk of transmission via breastfeeding of significant serious viral infections.  This page is not intended to be a comprehensive resource on all viral transmission issues, but highlights important clinical guidelines that may be useful to the GP.

In clinical practice, where a mother is at risk of transmitting a significant viral illness, we would expect the mother to be under specialist care, or for specialist advice to be sought. The information below is intended as a guide based on nationally and internationally recognised guidance, and is not intended to replace that of an individual’s specialist team. 

Please note- where the guidelines cited on this page recommend avoidance of breastfeeding during nipple fissuring, bleeding or mastitis. this advice is specific to the maternal conditions mentioned and should not be applied to the general population.


British HIV Association (BHIVA) Guidelines for management of HIV in pregnancy and postpartum 2018 (2019 interim update) (see section 9.4 p87-90 re: Infant Feeding). Current BHIVA Guidelines advise that in the UK and other high-income settings the safest way to feed infants born to women with HIV is with formula milk, as there is on-going risk of HIV exposure after birth. This position is taken because currently, data is lacking to apply the principle regarding HIV viral load of ‘undetectable=untransmissible’ to breastfeeding. In studies, suppressive maternal combination antiretroviral therapy (cART) significantly reduces, but does not completely eliminate vertical transmission (noteworthy that this data is not from high-income countries).

The guideline includes:

  • Supporting women living with HIV to formula feed, including the provision of formula milk and offering cabergoline to suppress lactation
  • Women living with HIV who choose to breastfeed being made aware of the small ongoing risk of HIV transmission during breastfeeding and supported to breastfeed if they fulfil the following criteria:
    • A fully suppressed viral load (for as long as possible, and at least for the last trimester of pregnancy)
    • A good maternal cART adherence history
    • Strong engagement with the perinatal multidisciplinary team
    • They are prepared for monthly clinical review and HIV testing for themselves and their infant whilst breastfeeding and for 2 months after cessation.
  • Women who do not meet the above criteria should be advised not to breastfeed and those who chose to breastfeed with a known detectable HIV viral load should have a social care referral
  • Women who choose to breastfeed are advised to:
    • Breastfeed for as short a time as possible
    • Exclusively breastfeed for the first 6 months
    • Introduce complementary foods as per standard UK guidance after 6 months
    • Cease breastfeeding if they develop a breast infection/mastitis
    • Cease breastfeeding if they or their baby develop gastrointestinal symptoms (due to the risk of cART malabsorption and an increased risk of HIV transmission via the GI tract respectively)
  • The importance of breastfeeding support, prevention of breastfeeding problems and ensuring mothers know how to access services promptly
  • Acknowledgement of the emotional, social and financial cost for mothers living with HIV who do not breastfeed

The guideline is also accompanied by leaflets for parents providing the rationale for current practise and information for breastfeeding mothers living with HIV on self-care and expressing milk.

BHIVA acknowledges that there is currently no data on the risk of HIV transmission via breast milk in high-income countries. The NSHPC (National Surveillance of HIV in Pregnancy and Childhood, UCL) is now collecting data from the UK and Ireland on women living with HIV who breastfeed their infants. This will contribute to epidemiological data in future.

WHO Updates on HIV and Infant Feeding 2016 – The World Health Organisation (WHO) provides guidelines for countries with high HIV prevalence and settings in which diarrhoea, pneumonia and undernutrition are common causes of infant and child mortality, but is also intended to be applicable to settings with a low prevalence of HIV depending on the background rates and causes of infant and child mortality. The latest recommendation for mothers living with HIV in these settings who are taking antiretroviral therapy (ART) and have no signs of immune or viral failure include:

  • Exclusive breastfeeding to 6 months
  • Introduction of complementary foods after 6 months alongside continued  breastfeeding for at least 12 months
  • Continued breastfeeding for up to 24 months or longer (similar to the general population)
  • While being fully supported for ART adherence

A summary of these recommendations can be found here.

It is important for GPs to be aware that in the UK a considerable proportion of pregnant women living with HIV will have come from countries and communities where breastfeeding is both the norm and a cornerstone of infant and young child survival, and in which avoidance of breastfeeding may result in disclosure of their HIV status2.  Additionally, women who are seeking asylum and have indeterminate right to remain in the UK may face difficulty obtaining formula milk and preparing it safely if returned to their countries of origin.  For such women breastfeeding may be the means whereby they can maintain their child’s food security. In such cases specialist input to safely facilitate breastfeeding in accordance with current infant feeding guidance, while strictly adhering to cART (combination antiretroviral therapy) is critical.

THEREFORE- If a UK mother with HIV chooses to breastfeed, specialist input can facilitate optimisation of the health of mother and infant with meticulous adherence to cART and skilled breastfeeding support.

Mothers living with HIV who do not breastfeed may find this emotionally, financially and socially challenging2. Non-judgemental support from healthcare professionals, peer mentorship and education around developing secure infant attachment are recommended2. Information on infant milks and safe bottle feeding should be provided, as well as signposting those eligible to the Healthy Start scheme.

WHO: Mastitis- Causes and Management 2000 – If a breastfeeding mother with HIV develops mastitis, a fissure or abscess, the WHO recommendation is that she should avoid breastfeeding from the affected side while the condition persists. Breastmilk should be expressed from the affected breast and not fed from that side until mastitis has resolved. Please see the linked document above for further detail.

La Leche League International: Update on HIV and Breastfeeding by Pamela Morrison IBCLC, April 2019 – Summarises issues around breastfeeding for mothers living with HIV.

The World Breastfeeding Trends Initiative (WBTi) Report 2016: Indicator 8 Infant Feeding and HIV (see pages 48-50) The WBTi 2016 UK report included an assessment of UK health professional training on infant and young child feeding (IYCF) against the WHO Education Checklist for Lactation. The report identified that misinformation on HIV and infant feeding is widespread, and that healthcare staff and community workers do not receive up-to-date training on the subject.

Hepatitis A

British Association of Sexual Health and HIV (BASHH): UK National Guideline on the Management of the Viral Hepatitidies A, B and C 2017 interim update of 2015 guideline – See Section 2.8.4. The Guidelines state “The risk [of Hepatitis A transmission] from breast feeding is uncertain, although there are no reported cases of transmission from breast milk. Even if the infant is infected, the disease is normally mild or asymptomatic. Therefore, the balance of risks between infection and stopping breast feeding should be considered on an individual basis”.

Hepatitis B

British Association of Sexual Health and HIV (BASHH): UK National Guideline on the Management of the Viral Hepatitides A, B and C  2017 interim update of 2015 guideline – See Section 3.8.5.  The Guidelines state “Infants born to infectious mothers are vaccinated from birth. Hepatitis B specific Immunoglobulin 200 IU IM is also given in certain situations where the mother is highly infectious. This reduces vertical transmission by 90%”.

US Centres for Disease Control and Prevention (CDC): Breastfeeding & Hepatitis B Infection Reviewed January 2018- States that the risk of HBV mother-to-child transmission through breastfeeding is negligible if infants born to HBV-positive mothers receive hepatitis B immune globulin and HBV vaccine within 12 hours of birth.  There is no need to delay breastfeeding until the infant is fully immunised.  Nursing should stop temporarily if the nipples are cracked and bleeding until healing occurs. Milk should be expressed and discarded during this period to maintain supply.  (See the link for further detail).

Hepatitis C

British Association of Sexual Health and HIV (BASHH): UK National Guideline on the Management of the Viral Hepatitidies A, B and C 2017 interim update of 2015 guideline- See Section 4.8.5: The Guidelines state “Breastfeeding: there is no firm evidence of additional risk of transmission”.  However, unlike Hepatitis B “there is no clearly demonstrated intervention to reduce HCV transmission from mother-to child” and “Women should be informed of the small potential risk of transmission in pregnancy“. “Vertical (mother to infant) spread also occurs at a low rate (about 5%), but higher rates (7% or more) are seen if the woman is co-infected with HIV. In all groups transmission risk correlates with the quantity of detectable HCV-RNA in the mother’s blood”.

The Hepatitis C Trust: Hepatitis C Information for Women States breastfeeding is considered safe but recommends avoidance of breastfeeding if there is active nipple bleeding, until healing occurs.

US Centres for Disease Control and Prevention (CDC): Breastfeeding & Hepatitis C Infection Reviewed January 2018 – States there is no data to suggest HCV transmission occurs via breastfeeding. Nursing should stop temporarily if the nipples are cracked and bleeding until healing occurs. Milk should be expressed and discarded during this period to maintain supply.  (See the link for further detail).

Zika Virus

RCOG/RCM/PHE/HPS Clinical Guidelines: Zika Virus Infection and Pregnancy- Information for Healthcare Professionals Updated 27/2/19 – States “Viable virus has been detected in breast milk and possible Zika virus infections have been identified in breastfeeding babies but Zika virus transmission through breast milk has not been confirmed. Therefore, the benefits of breastfeeding are likely to outweigh the risks of Zika virus infection in infants” (See section on ‘Transmission’). These guidelines are accessed at RCOG: Zika Virus Infection and Pregnancy.

WHO: Infant Feeding in Areas of Zika Virus Transmission Last update February 2019 – “Infants born to mothers with suspected, probable or confirmed Zika virus infection, or who reside in or have travelled to areas of ongoing Zika virus transmission, should be fed according to normal infant feeding guidelines. They should start breastfeeding within one hour of birth, be exclusively breastfed for six months and have timely introduction of adequate, safe and properly fed complementary foods, while continuing breastfeeding up to two years of age or beyond”.  The WHO has further guidance here.

NHS Website: Zika Virus Includes information for pregnant women and information on reducing the risk of Zika infection. States it is safe to use up to 50% DEET while pregnant and breastfeeding, and for infants and children over 2 months old. Also has a link to up to date information from Public Health England on Zika.


  1. Unicef UK Baby Friendly Initiative: Three-day Course in Breastfeeding Management Participant’s Handbook (2008)
  2. Tariq S, Elford J, Tookey P, et al “It pains me because as a woman you have to breastfeed your baby”: decision-making about infant feeding among African women living with HIV in the UK 

Published April 2017, Updated April 8th 2020