Neonatal herpes or HSV is a rare, but potentially fatal, disease of babies which usually occurs in the first four weeks of life.


It is caused by the herpes simplex virus (HSV) which is a very common and highly contagious virus which in older children and adults can cause cold sores and genital ulcers but often has no symptoms at all.


Early recognition, a high index of suspicion and prompt treatment are essential to save the baby's life. 

If a mother contracts the herpes virus before she is pregnant or by the second trimester then her baby will very likely be protected against the virus. 


There are some things you can do to help prevent transmission of herpes to a young baby such as regular hand washing, covering cold sores and not kissing babies who are not your own.


The herpes infection in a baby is called neonatal herpes or neonatal HSV. It is typically divided into three categories:

  • Infection of the skin, eyes and mouth (SEM)

  • Infection involving the brain (central nervous system/CNS)

  • Infection of multiple organs such as lung, liver, adrenal glands, brain and skin (disseminated)

In young babies who have immature immune systems; left untreated, HSV infections can spread rapidly, causing irreversible cell damage which can lead to permanent disability or death.

Early recognition and prompt treatment with antiviral medication is essential to save the baby's life. Even if treated, a baby may suffer permanent brain damage or die.



Herpes simplex virus (HSV) is a very common and highly contagious virus which usually spreads from person to person by direct contact. HSV is carried by around 70% of adults in the UK (1).​

Many carriers have no symptoms at all but in others it can lead to cold sores, blisters on the finger (called herpetic whitlow) or genital ulcers/sores. Infections of other areas including the breast are also possible but less common. In older children and adults with normal immune systems, HSV infections are not normally serious and will get better without treatment but if left untreated in young babies it is life-threatening. 

There are two types of HSV: type 1 (HSV-1) and type 2 (HSV-2):

  • HSV-1 is mainly contracted by oral-to-oral contact to cause oral herpes (usually manifests as cold sores) and can also be transmitted through oral sex to cause genital herpes.

  • HSV-2 is mainly sexually transmitted and causes genital herpes.

Herpes infections are most contagious when symptoms are present but can still be transmitted to others in the absence of symptoms as the virus can shed at any time. Once someone contracts an HSV infection, the virus remains in the body for life. The initial infection is usually the most severe. 

You can read more about the herpes simplex virus in this World Health Organization factsheet.



Babies can become infected in one of three ways:

  • During a vaginal birth 'perinatal': through contact with HSV infected secretions in the birth canal. This is the most common source of infection.

  • Contact with the virus after birth 'postnatal': through direct exposure to an active herpes infection on anyone who comes into close contact with the baby, including caregivers and healthcare professionals.

  • In the womb 'in-utero': through the placenta or cervix. This type of infection is rare, accounting for less than 5% of all neonatal herpes infections.

When a mother is already an HSV carrier before conception or becomes infected in the first 6 months of pregnancy the baby will be most likely be protected as the antibodies to fight the virus will have been passed though the placenta to protect the baby after delivery.​ 


The risk of herpes being passed to the baby during birth is greatest when the mother acquires an HSV infection for the first time in the third trimester of pregnancy. Symptoms can be very mild or absent so can be missed or put down to another cause.


The risk for postnatal transmission is highest when the mother does not carry the virus or has been very recently infected. This is because there has not been time for the mother to develop and pass antibodies across the placenta. Postnatal transmission is usually but not always from someone who has an active cold sore, HSV infected broken skin or blisters on the fingers due to HSV (herpetic whitlow). It can be passed on by a kiss or by someone touching an active infection then touching the baby. It can also be passed to the baby from a breastfeeding mother with an HSV infection in the breast/nipples.

As many carriers of the virus will have no symptoms, a baby may get infected without coming into contact with any lesions at all therefore medical professionals must have a high index of suspicion of HSV infection when seeing an unwell baby in order to treat them quickly enough.



Babies with an HSV infection can become unwell very quickly but the early symptoms may not be very obvious. Signs of infection in a baby include:

  • Lethargy​/extreme tiredness

  • Irritability

  • High-pitched or abnormal cry

  • Poor feeding

  • High temperature

  • Floppiness

  • Grunting or difficulty breathing

  • Rash or sores on the skin, eye or inside the mouth (but not all babies will have lesions when thy first become unwell)


If you are concerned ​your baby has an infection, seek medical assistance as soon as possible and always ask 'Could it be herpes?'

  • If your baby has any of the following call 999 immediately:

    • Any change in colour (very pale, blue or dusky)​

    • Difficulty breathing (noisy grunts, rapid breaths, ineffective breathing, pauses between working hard to breathe)

    • Regular jerking of the arms and legs like a fit


An antiviral medication is administered into the baby's blood stream (intravenously) typically for 14-21 days. Some babies may require longer treatment. The most commonly used medication is called acyclovir. Because babies have small, fragile veins it can be difficult to deliver this medication through a normal cannula (drip) so some babies will have a semi-permanent drip inserted to help give the medication. This will be removed once treatment with intravenous medicine has finished.

Longer term oral antiviral medication might be prescribed after the initial treatment course to reduce the risk of a recurrence.

Treatment must be given promptly in order to be successful. Babies who are not given antiviral medication quickly may very sadly die.

Some babies make a full recovery if they have been given early treatment but, even with treatment, if the infection has spread to the baby's organs it may result in permanent brain damage or death.



Sometimes the herpes virus will be passed on without any symptoms but there are some things you can do to reduce the risk.

If you are pregnant:

  • If you have ever had genital herpes (ulcers/blisters/sores) in the past or develop symptoms during your pregnancy then let your doctor/midwife know. They may prescribe oral antiviral medication. 

  • If you develop genital herpes for the first time during your last trimester then a cesarean birth may be recommended which significantly reduces the risk of transmission during delivery. 

  • If you are not a known carrier of HSV you should refrain from receiving oral sex in the last trimester of pregnancy.

If you are breastfeeding:

  • If you develop lesions on your breast or nipples you should stop feeding from that breast immediately and arrange to see your GP as soon as possible. The lesions should be tested for HSV and treated accordingly.

If you have a cold sore, herpetic whitlow or infected broken skin:

  • You should try and avoid direct contact with newborn babies who are not yours to avoid putting them at risk. If you are the parent or main caregiver or contact is unavoidable you should ensure the lesions are covered and wash your hands thoroughly and regularly. The lesions should be treated with topical acyclovir cream until they heal over.

  • Healthcare workers with cold sores or skin lesions should avoid handling newborn babies.

  • If you are the mother and know you carry HSV please remember your baby is very likely to be protected against new infections.

Everyone coming into contact with a newborn baby:

  • As people can shed the virus with no symptoms, everyone should wash their hands carefully before holding a young baby. Regular and thorough hand washing is essential. Handwashing advice is given below. 

  • Nobody other than the parents should kiss a newborn baby especially if they have a cold sore. Even parents with a cold sore should not kiss their infants until the lesion has healed over.


Washing hands thoroughly can be a very effective way of preventing the herpes and other viruses passing from person to person including to a newborn baby.

Parents should wash their hands often including on arrival at home and before and after changing the baby's nappy. Visitors to a new baby should also wash their hands on arrival and before holding the baby.


Hands should be washed with soap and water for at least 20 seconds to effectively remove the virus. If soap and water are not available alcohol-based hand sanitiser should be used. Washing your hands properly takes about as long as singing "Happy Birthday" twice using the technique below:



  1. BASHH: 70% of the UK population are infected with HSV1 or HSV2 by the time they are 25 years old

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