An epidemic of "nonparalytic poliomyelitis-like" illness which occurred in Marshall-town, Iowa during the summer of 1955 is reported. The attack rate was greatest among children (30.8%) and decreased with increasing age. The average attack rate was 16% and approximately 3,200 cases of illness occurred. Headache, fever, and stiff neck or back were the major symptoms. Other complaints included myalgia, sore throat, nausea, vomiting, diarrhea, irritability and weakness. Examination of the cerebrospinal fluid revealed an average cell count of 200/mm3 with a preponderance of lymphocytes, normal or slightly elevated content of protein, and normal content of sugar. Convincing evidence is presented which establishes ECHO virus type 4 as the etiologic agent in this outbreak.
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