Neonatal herpes (Neonatal HSV)

Herpes simplex virus (HSV) infection in a newborn baby is called ‘neonatal herpes’ or ‘neonatal HSV’.

HSV is a very common and highly contagious virus which usually spreads from person to person by direct contact.

There are two strains of the HSV virus:

• HSV-1 (or Type 1) mostly spreads by oral contact and causes infections around the mouth
• HSV-2 (or Type 2) mostly spreads by sexual contact and causes infections around the genitals

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

In young or premature babies who have immature immune systems, HSV infections can spread rapidly if left untreated, 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 could suffer permanent brain damage or die if they are not treated quickly enough.

Babies can become infected in two main ways:

• During a vaginal birth (perinatal): through contact with HSV 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 very rare case, babies can also become infected inside the womb (also called 'in-utero') through the birth parent's placenta or cervix.

How can a baby become infected with herpes during birth?

Mothers and birth parents who have had genital herpes before getting pregnant, or who have their first infection early in pregnancy, are very unlikely to pass an infection on to their baby during delivery.

This is because, over time, the birth parent develops protective ‘antibodies’ (immune system proteins) which will then pass across to the baby during pregnancy.

Babies are most at risk from neonatal herpes if the birth parent contracts genital HSV (HSV-2) for the first time during the third trimester of pregnancy (28-40+ weeks). This is because a newly infected birth parent has not had time to develop antibodies against the herpes virus 2.

Babies born very prematurely (at or before 28 weeks) are also more at risk. This is because the birth parent's antibodies have not had long enough to pass to the baby.

If there is a known first episode of genital herpes in late pregnancy, birth parents may be advised to have a caesarean section (also called a 'c-section') to minimise the risk of transmission to their baby.

How can a baby catch herpes after birth?

Infection after birth usually occurs following contact with an active cold sore, HSV-infected broken skin or HSV blisters on the fingers (herpetic whitlow).

Infection can be passed on directly (for example, by a kiss) or indirectly (for example, by touching an area with active infection and then immediately touching the baby). It can also be spread during breastfeeding if the birth parent has an HSV infection on their breast or nipple.

Babies are at greatest risk of transmission after birth if they do not have antibodies which protect them from the virus. This happens when the birth parent has not had an HSV infection before becoming pregnant, or if they have their first infection in late pregnancy. This is because there has not been time for the birth parent to develop and pass antibodies to her baby.

Babies born to birth parent’s who have had an oral (HSV-1) infection (for example, cold sores) before they reach their third trimester are much more likely to be protected from acquiring the infection after birth.

Babies born very prematurely (at or before 28 weeks) are also more at risk because the birth parent’s antibodies have not had long enough to pass through the placenta to the baby.

Babies with an HSV infection can become unwell quickly, but the early symptoms may not be very obvious.

There is no clear pattern of signs and symptoms that makes it obvious a baby has neonatal HSV. This means that herpes should be considered in all unwell babies in order to treat them quickly enough.

Signs of infection in a baby include:

• Lethargy​/extreme tiredness

• Irritability

• High-pitched or abnormal cry

• Poor feeding

• Abnormally high or low temperature

• Floppiness

• Grunting or difficulty breathing (you may notice the baby 'sucking in' between and underneath their ribs)

• Rash or sores on the skin, eye or inside the mouth* (but not all babies will have signs on their skin when they first become unwell)

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

• Any change in colour to very pale, blue or dusky

• Noisy and/or rapid breathing, ‘sucking in’ between or under the ribs, pauses between breaths

• Regular jerking of the arms and legs like a fit

If your baby has a rash or blisters that you are unsure about, it is important to ask for advice from your doctor or midwife.

Babies with localised HSV infection on their skin, eyes or mouth may otherwise appear well, but these infections can quickly spread and cause them to become seriously unwell if left untreated.

It can also be more difficult to spot signs of neonatal herpes in babies with Black, Brown or darker skin tones. For some photos of what these symptoms can look like, visit Skin Deep’s website - Herpes siplex virus - Skin Deep.

An antiviral medication is given by injection into a medical drip (a thin tube inserted into a vein), typically for 14–21 days, although some babies may require longer treatment. The most commonly used medication is called 'acyclovir’ (pronounced ‘assey-clove-eeyer’).

Longer term oral antiviral medication might be prescribed after the initial treatment to reduce the risk of a recurrence 2.

Treatment must be given promptly in order to be successful. Babies who are not given antiviral medication quickly may become extremely unwell.

​Many babies make a full recovery but, even with treatment, if the infection has spread to the baby's organs it may result in permanent disability or death.

Because some herpes infections do not produce symptoms, the virus can be passed on without anybody realising, but there are some simple things you can do to reduce the risk.

If you are the mother and know you carried HSV before your third trimester, please remember your baby is likely to be protected against new infections.

If you are pregnant

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

• If you develop genital herpes for the first time during your last trimester, then a caesarean birth may be recommended which significantly reduces the risk of transmission during delivery. It is very important to tell your doctor of midwife if this is the case.

• If you are not a known carrier of HSV you should refrain from receiving oral sex in the last trimester of pregnancy especially if your partner has had cold sores in the past.

• If your partner has active lesions, you should avoid sexual activity in late pregnancy to reduce the risk of catching HSV. Using barrier protection (male or female condoms) can also reduce the risk but it is not 100% effective.

If you are breastfeeding

• If you develop lesions on your breast or nipples you should stop feeding from that breast immediately 2 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, blister on the fingers (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.

Everyone coming into contact with your 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 virus and other viruses and bacteria 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 of 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.