Persistent rubella-specific IgM reactivity in the absence of recent primary rubella and rubella reinfection

Between two and seven sera from cases of persistent detection of rubella-specific IgM for periods in excess of 2.5 months, but in the absence of recent primary rubella or rubella reinfection, were examined for rheumatoid factor, heterophile antibody, and IgM reactivity against toxoplasma and a number of viruses. The relative avidity of the rubella-specific IgG1 has been assessed in all the sera by two methods. None of the sera contained rheumatoid factor or heterophile antibody, nor did any contain detectable concentrations of IgM specific for any of the panel of antigens apart from five sera which contained low concentrations of IgM specific for some coxsackieviruses B. No sera were positive for low avidity specific IgG1 although three did give equivocal results with one avidity test and one gave equivocal results with the second avidity test.