SUMMARY Coxsackie A9 virus was isolated from a neonate presenting with a massive pericardial effusion. Delivery had occurred after maternal infection. The virus was cultured from the cerebrospinal fluid, urine, and faeces of the infant and from the faeces of the mother and a sibling. Despite signs of generalised infection with pericarditis, meningitis, pneumonitis, and hepatitis, recovery was complete.Enteroviral infections in neonates are relatively common. Of the infections caused by the enterovirus group over 90% are due to echoviruses and Coxsackie B viruses and a small minority to Coxsackie A viruses. Although seldom encountered, this latter virus may cause a severe illness with a fatal outcome. Even then, cardiac involvement is rare. ' We report the case of a neonate with generalised Coxsackie A9 viral infection presenting with a massive pericardial effusion who fully recovered.Case report A 6 day old male infant was referred because of progressive cardiomegaly. The infant was born after a pregnancy of 33 weeks' gestation. The mother was 28 years old, gravida 2. In the week before delivery both the mother and a sibling had pyrexia, diarrhoea, and a transient rash on the trunk. Labour started, and after three days a male infant was born (weight 2.4 kg) despite the intravenous administration of ritodrine hydrochloride. The Apgar scores were 5 and 6 after one and five minutes respectively. Because of respiratory distress with hypercapnia and acidosis the child had to be intubated and ventilated with a high inspired oxygen content. An arterial umbilical catheter was inserted and ampicillin and gentamicin were given prophylactically. After 40 hours the infant was extubated. Because of an inspiratory stridor and possible glottal oedema dexamethasone was given intravenously. At the age of 5 days the infant's condition suddenly deteriorated. His temperature rose to 38-50C, and he had diarrhoea and a generalised rash. Sepsis was suspected and blood cultures were performed. Antibiotic treatment was changed to penicillin and chloramphenicol. On the sixth day a chest radiograph showed cardiac enlargement.On admission to this hospital the child was pink and breathing 30% oxygen. He was slightly tachypnoeic. The peripheral arterial pulses were normal, and there was no pulsus paradoxus. Systolic blood pressure in the right arm was 75 mm Hg. No murmurs were heard, and the heart sounds were clear. Hepatomegaly' was present (3 cm below the right costal margin). Neurological examination was normal and no rash was seen.The following laboratory data were obtained: white blood cell count 15 300/mm3 with 78% polymorphonuclear leucocytes and 11% band forms. Arterial blood gas analysis showed pH 7-22, Pco2 7.86 kPa (59 mm Hg), Po2 8.93 kPa (67 mm Hg), and sodium bicarbonate concentration 22 mmol/l. Electrolytes and urea and creatinine concentrations were within normal limits. Serum aspartate aminotransferase and serum alanine aminotransferase activity was normal, on admision but raised after two days (103 IU/1, and 111 IU/l resp...