Neonatal herpes is known as the "kiss of death".
But as we learned from the tragic case of baby Eibhlín Wills, the herpes virus can be passed on in different ways to an infant, even without a kiss.
Neither of her parents had the virus - and she picked it up in hospital.
Neonatal herpes is an infection in a newborn baby.
It is caused by the herpes simplex virus, a highly contagious disease that can cause cold sores and genital ulcers in adults.
Herpes can be very serious for a young baby, whose natural defences have not developed.
An infant is at risk of catching if the mother had genital herpes for the first time within the last six weeks of pregnancy.
There's a risk the mother will have passed the infection on to her baby if she had a vaginal delivery.
The virus can also be passed on to a newborn baby if a person has a cold sore and kisses the child.
Virologist Prof Cillian de Gascun said yesterday it can also be passed on by someone who has the virus but is not displaying symptoms or have a cold sore.
Newborns can end up becoming seriously ill very quickly, becoming lethargic or irritable, not feeding and having a high temperature.
There can also be a rash or sores on the skin, eyes and inside the mouth.
It is usually treated with antiviral drugs.
It will become a notifiable disease in Ireland shortly, so all cases will be reported.
If someone has a cold sore or think they are coming down with a herpes infection, they're warned:
:: Do not kiss any babies;
:: Make sure to wash your hands before contact;
:: Wash hands before breastfeeding and cover up any cold sores, to avoid accidentally touching your mouth and then breast, and transferring the virus.