OBJECTIVE Severe Epstein-Barr (EB) virus infection is potentially a devastating process that often leads to death encountered in pediatrics recently. Inappropriate control of EB virus replication may cause severe infection resulting in multiple organ dysfunction. However, little information is available on pulmonary complications associated with EB virus infection. The aim of the present study was to investigate severe EB virus (EBV) infection complicated with lung injury in pediatric intensive care unit (PICU), including clinical characteristics, laboratory or imaging feature and outcomes. METHODS A total of 45 children with severe EBV infection seen in PICU of Shanghai Children's Hospital between January 2011 and December 2014 were retrospectively reviewed. According to clinical characteristics and imaging feature, 45 children were divided into non-lung injury group (n =27), lung injury without pulmonary fibrosis group(n = 12) and pulmonary fibrosis group (n = 6). RESULTS In totally 45 cases of severe EBV infection, 21 (46.7%) were male and 24 (53. 3%) were female, mean age was 2. 4 years; 18 cases were complicated with lung injury, including 8 male and 10 female, median age was 31. 2 months. All of 18 cases presented with fever and cough, 15 of them exhibited dyspnea,12 cases were complicated with gasping, and 6 cases with ARDS. Eight cases accepted mechanical ventilation for acute respiratory distress; 6 cases who developed pulmonary fibrosis had tachypnea, refractory hypoxemia and hypercapnia, severe pulmonary air leak. The average EBV-DNA level in peripheral blood was 4. 42 x 10(6) copies/ml (range: 3. 25 x 10(3) - 6.59 x 10(7) copies/ml). Anti-EBV antibodies were positive in 41 cases, 18 cases were positive (+) for VCA-IgM, 15 cases were VCA-IgG and EA-IgG (+), 8 cases VCA-IgM and VCA-IgG (+). The radiographic findings revealed pulmonary interstitial infiltrates in all 18 cases with lung injury, 4 cases with segmental consolidation and 2 cases showed pleural effusions. HRCT scanning found EBV associated fibrosis including multifocal patches and diffuse ground-glass attenuation in both lungs, reticular opacities and honeycombing changes were observed 4 weeks after illness onset. There were significant differences in respiratory failure, PICU stay (days), Pediatric risk of mortality III (PRISM III) and pediatric clinical illness score(PCIS), serum TNF-α, EBV-DNA levels, percentage of NK cells and CD4+/CD8+ T cell ratio among non-lung injury group, lung injury without pulmonary fibrosis group and pulmonary fibrosis group (X2 =27. 12, F = 85. 23, 78. 23, 88. 68, 323. 80, 7. 35, χ2 = 6. 71, 12. 15; all P < 0. 05). COX regression analysis revealed that EBV-DNA and serum TNF-α levels were correlated with pulmonary fibrosis significantly (OR = 3. 92, P = 0. 04; OR = 5. 95, P = 0. 01). The patients with EBV-associated hemophagocytic lymphohistiocytosis (EBV-HLH) had higher incidence of pulmonary fibrosis compared with non-EB-HLH (70% vs. 13%, χ2 = 4. 82, P = 0. 03). Of 18 cases, 8 cases died, including 3 cases with pulmonary fibrosis. The surviving cases with pulmonary fibrosis needed longer additional oxygen. Chest HRCT imaging of 3 cases with pulmonary fibrosis was improved at 6 months and oxygen therapy was discontinued at 18 months after discharge. CONCLUSIONS EB virus infection complicated with lung injury had higher incidence of respiratory failure, pulmonary fibrosis with a fatal outcome. EBV-DNA and serum TNF-α level were found to be statistically significant indicators of pulmonary fibrosis. Pulmonary fibrosis associated with severe EB virus infection may be reversible.