The World Health Organization has warned of an “unusual” increase in cases of severe myocarditis associated with enterovirus infection among very young babies in south Wales. Between June 2022 and April 2023 10 babies under 28 days of age presented with symptoms of myocarditis at a tertiary hospital in south Wales and tested positive for enterovirus on PCR testing. Seven babies were treated in intensive care, and one died before transfer to tertiary care. One infant is still being treated in hospital. The peak incidence was in November 2022, with sporadic cases in other months. Seven of the 10 cases had further subtyping, which identified the enterovirus as either coxsackievirus B3 or coxsackievirus B4. A further five babies have been identified with myocarditis and enterovirus infection over …