Epidemics of Mycoplasma pneumoniae infection in Denmark from 1958 to 1974.

The study is a retrospective and prospective serological investigation of the incidence of Mycoplasma (M.) pneumoniae infection in Denmark during a 17-year period. By least square multiple regression analysis it was shown that four major outbreaks or epidemics had occurred which culminated at regular intervals of four and a half years. The study was based on cold agglutinin (CA) positive sera tested for antibodies to M. pneumoniae by an indirect immunofluorescence (IF) test, an indirect haemagglutination (IHA) test or a complement fixation (CF) test. By the criteria chosen for a positive test, the CF test was found to detect more cases than the IF or IHA tests. A shift during the study from the latter two tests to the CF test influenced the incidence, but not the periodicity of epidemics. The consequence of including only CA positive sera in the study was investigated.