Elevated creatine phosphokinase levels associated with influenza A/Texas/1/77 infection

24 patients admitted to hospital between December 1, 1977 and March 3, 1978 with cultural or serological evidence of influenza A infection were retrospectively analyzed for evidence of elevated creatine phosphokinase (CPK) levels. 14 patients had elevated CPK levels not attributable to usual causes. Muscle biopsies from 2 patients showed focal necrosis and myopathic changes. Influenza A/Texas/1/77 was isolated from the biopsy specimen of 1 patient. Patients with elevated CPK levels tended to have greater per day hospital costs and more complications than patients with normal CPK levels. Elevated CPK levels are relatively common in hospitalized patients with influenza and may be due to influenza virus involvement of skeletal muscle.