Histopathological evaluation showed myocarditis in a higher than expected proportion of cases. In one such case, which we studied before the sudden unexpected death occurred, the victim had suffered a Chlamydia pneumoniae infection verified by serology, and a nucleotide sequence was found in the heart and lung by means of the polymerase chain reaction (PCR) that hybridized with a probe specific for that organism. Male Swedish orienteers do not, however, seem to have an increased rate of exposure to this agent. No further sudden unexpected deaths among young orienteers have occurred over the past 3.5 years. At the beginning of that period, attempts were made to modify training habits and attitudes.

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Swedish guidelines for diagnosis and treatment of infective endocarditis (IE) by consensus of experts are based on clinical experience and reports from the literature. Recommendations are evidence based. For diagnosis 3 blood cultures should be drawn; chest X-ray, electrocardiogram, and echocardiography preferably transoesophageal should be carried out. Blood cultures should be kept for 5 d and precede intravenous antibiotic therapy. In patients with native valves and suspicion of staphylococcal aetiology, cloxacillin and gentamicin should be given as empirical treatment. If non-staphylococcal etiology is most probable, penicillin G and gentamicin treatment should be started. In patients with prosthetic valves treatment with vancomycin, gentamicin and rifampicin is recommended. Patients with blood culture negative IE are recommended penicillin G (changed to cefuroxime in treatment failure) and gentamicin for native valve IE and vancomycin, gentamicin and rifampicin for prosthetic valve IE, respectively. Isolates of viridans group streptococci and enterococci should be subtyped and MIC should be determined for penicillin G and aminoglycosides. Antibiotic treatment should be chosen according to sensitivity pattern given 2-6 weeks intravenously. Cardiac valve surgery should be considered early, especially in patients with left-sided IE and/or prosthetic heart valves. Absolute indications for surgery are severe heart failure, paravalvular abscess, lack of response to antibiotic therapy, unstable prosthesis and multiple embolies. Follow-up echocardiography should be performed on clinical indications.

Acute infections are associated with multiple host responses that are triggered by cytokines and correlated to fever, malaise and anorexia. The purpose of this systemic acute phase host reaction ("the acute phase response") is to mobilize nutrients for the increased needs of the activated immune system, as well as for energy production and tissue repair. Important effects include wasting of striated muscle, degradation of performance-related metabolic enzymes and, concomitantly, deteriorated central circulatory function. These effects result in decreased muscle and aerobic performance, the full recovery of which may require several weeks to months following week-long febrile infections. Also during early infection and fever, prior to the development of muscle wasting, performance is compromised by other mechanisms. Strenuous exercise may be hazardous during ongoing infection and fever and should always be avoided. In infection, muscle wasting seems to be less pronounced in the conditioned (trained) host than in the unconditioned host. Acute myocarditis most often has a viral etiology but bacteria and their toxins may also be the cause. Furthermore, slow-growing bacteria, previously difficult to diagnose, have emerged as potential "new" causes of subacute to chronic myocarditis. Since myocarditis may or may not be associated with fever, malaise, or catarrhal symptoms, athletes should be taught the symptoms suggestive of myocarditis. Whenever myocarditis is suspected exercise should be avoided.