Prevalence of antibody to the Norwalk virus in various countries
Serum samples from children and adults from several countries were tested by radioimmunoassay for antibody to the Norwalk virus. Antibody was commonly found in adults from all the countries tested. Antibody appears to be acquired more rapidly in children from underdeveloped countries than in children from the United States.
Infect Immun 1979 Oct;26(1):270-3