Medulloblastomas are the most common malignant brain tumours in children. This paper showed that a large proportion of primary medulloblastomas are infected with human cytomegalovirus (HCMV), and the virus directly modulates the expression of cyclooxygenase 2 (COX2) and levels of prostaglandin E2 (PGE2). A combination of the antiviral drug valganciclovir and the COX2 inhibitor celecoxib prevented HCMV replication in neuroblastoma cells, and it inhibited PGE2 production and reduced medulloblastoma tumour growth in mice, implying that targeting HCMV is beneficial in medulloblastoma.