Written Statement: Ongoing investigation into neonatal myocarditis cluster in South Wales

A cluster of severe enterovirus infections with myocarditis (inflammation of the heart muscle) occurring in very young babies from the South Wales region, is being investigated by Public Health Wales, working closely with the paediatric team at the Children’s Hospital for Wales.

The cases occurred from June 2022, with a peak in November 2022, involving babies under 28 days old. Enterovirus is a common infection of childhood which can cause a range of symptoms. It rarely affects the heart, with most babies and children recovering completely.  However, in very young babies, enterovirus can cause severe illness in the first few weeks of life.  

Ten babies have developed myocarditis within this cluster – one baby remains in hospital; eight are being managed as outpatients and, very sadly, one baby died. The families are being supported during this difficult time, and my thoughts are with all of them.

Parents should be reassured that although there has been an increase in cases, this is still an extremely rare occurrence. Paediatricians in Wales have been advised and will continue to consider the possibility of myocarditis in babies presenting with sepsis (blood poisoning). Wales has a good surveillance system in place for enterovirus and is engaged in a clinical study to understand this incident further and learn lessons, including changes in how infections circulate and population immunity following the pandemic.

The World Health Organisation has been informed about the cluster by Public Health Wales, under its International Health Regulations obligations because of the unusual and severe nature of the cases.