A previously healthy woman was admitted to hospital after 'flu-like' symptoms for 5 days followed by acute intense abdominal and lower back pain. On admission she was found to be in severe shock and was transferred to the ICU. Echocardiography revealed cardiac tamponade, and pericardiocentesis was performed immediately. Thereafter her cardiovascular state improved, but she developed hypotension with low systemic vascular resistance and required vasoactive treatment for 4 days. Nine days after admission the patient was transferred to the ward, after which she recovered rapidly and completely. The cause of her illness was extensively screened. No underlying disease was found, and all bacterial cultures remained negative. Acute virus infection was confirmed by diagnostic elevations of antibody titers to Influenza A and adenovirus. Adenovirus was also isolated from her bronchoalveolar lavage fluid.