To the Editor.—
Madden et al (Archives 1981;38:209-210) presented an interesting and careful study of antibodies to coronaviruses in the sera of patients with multiple sclerosis (MS) and controls. However, for a number of reasons we do not agree that their data, based entirely on a serologic survey, warrants the conclusion that "coronaviruses do not appear to be associated with the cause of MS."First, as the authors pointed out, coronaviruses are ubiquitous in man. This fact accounts for the high incidence of seropositivity in controls and may make it difficult to identify patients with disease, ie, nervous system involvement, against the background of general seropositivity. This is the case, for example, with conditions such as progressive multifocal leukoencephalopathy1 in which both affected patient and control populations have a high percentage of persons with antibody to the relevant virus, thus making diagnosis on serologic grounds impossible.Second, analysis of