PUUV serology was initially negative, but seroconversion occurred during the first week with development of positive immunoglobulin M (IgM) and IgG. No PUUV RNA could be detected in serum or bronchoalveolar lavage fluid, sampled two days after onset of disease. At autopsy PUUV RNA was detected in lung tissue, but not in samples from heart, brain, spleen and liver. Sequencing of the PUUV RNA from lung tissue showed that it was homologous to PUUV strains circulating in northern Sweden. No PUUV antigen could be detected in the tissue by immunohistochemistry using PUUV specific monoclonal antibody. Relevant bacterial cultures were all negative. Notably, three weeks prior to ICU admission the patient had sought medical treatment at our clinic for a urinary tract infection caused by E. coli. In the serum collected at that time PUUV RNA (1,700 copies/ml) was later detected. WBC white blood cell count (normal range 3.5-8.8×10 9 /L), TPC thrombocyte particle count (normal range for women 165-387 and for men 145- Autopsy revealed oedematous and atelectatic lungs with no normal aerated tissue. Pulmonary histopathological features consisted of diffusely oedematous parenchyma with interstitial and intraalveolar fibrosis. The alveoli contained exudates of fibrinous fluid, high number of alveolar macrophages (CD68 + ), proliferative epithelial cells and thick septa but without characteristic hyaline membranes. Interstitial mononuclear cell infiltrates were common, consisting mainly of CD3 + T lymphocytes whereof a vast majority was CD8 + . Many mononuclear cells were expressing cytotoxic markers granzyme B and T cell restricted intracellular antigen-1, TIA-1 (Fig. 2) . In pulmonary vessels, focal thrombosis was evident. Microscopy of the heart showed thrombosis in small vessels and focal massive infiltrates of granulocytes and macrophages. In the brain there was focal vasculitis, perivascular infiltration of CD8 + T lymphocytes and non-occlusive thrombosis. Infarctions were seen in the brain, lungs and spleen. Notably, the kidneys had no prominent inflammatory infiltrates.