There are many issues involved here.  There are several herpes viruses,
but I presume you mean Herpes Simplex.  There is also herpes zoster,
varicella virus (the latter two are the same), herpes virus 6, which
causes various viral syndromes in children, sometimes in pregnant women.

The question of herpes simplex, however, depends on how old the baby is,
and where the lesions of the infection are, or even if the lesions are
active, as herpes infection can be dormant.

Herpes simplex is most dangerous to the infant during the first month of
life, when they are most liable to develop systemic herpes which can be
fatal.  However, herpes simplex is passed on by direct contact.  Thus,
if the mother has active lesions on the cervix, breastfeeding is
unlikely to be of any issue.  However, if the mother has lesions on the
nipple, the baby of a young age should not nurse on that side.  If the
lesions are on the mother's lip, as long as the mother avoids touching
the lesion and then touching the baby, there should be no risk.

Of course, breastmilk contains antiviral factors which may protect the
baby against developing primary and/or systemic infection.

Medications used to treat the mother, such as acyclovir, are *not*
contraindications to breastfeeding.

In general, one can say that the mother can breastfeed.

Jack Newman, MD, FRCPC