A two year serological surveillance of coronavirus infections in Hamburg

The occurrence of OC-43 coronavirus-like infections in the population of Hamburg was determined by a monthly serological survey (hemagglutination inhibition test [HI]) undertaken between October 1974 and October 1976. Studies of 3,016 sera revealed a high incidence of HI antibodies (58.2%). The frequency of seropositive reactions (=1:8) and the geometric mean titer were higher in individuals 15 to 24 years old. Treatment of 50 positive sera (titer 1:16 – 1:64) with receptor destroying enzyme, kaolin and ethacridin for elimination of nonspecific inhibitors did not modify the HI-titer of the investigated sera. The serological seasonal pattern suggests that coronaviruses are circulating the whole year in the urban population with a prevalence in the fall-winter period. Of the 331 paired sera examined, 6.6% presented a four- to eightfold rise in titer within eight weeks.