Hypersensitivity pneumonitis and Legionnaires' disease.

Four outbreaks of Legionnaire's disease (LD) and numerous instances of hypersensitivity pneumonitis (HP) have been associated with contaminated water in air-conditioning and cooling tower systems. The present study was carried out to determine if antibody to Legionella pneumophilia (LP) could be detected in the serums of persons with HP related to air-conditioning and cooling tower systems, thus suggesting a possible relationship between the 2 diseases. Serums from 209 persons with suspected or confirmed HP were examined for antibody to LP by the microagglutination method. The results of only 3 serum tests were positive; these serums were from persons with respiratory symptoms suggestive of HP from air-conditioning and cooling tower systems, but who lacked clinical and laboratory confirmation of the disease. The results of all serum tests from confirmed cases of HP were negative. The results indicate that there probably is no association between the organisms causing LD and those associated with HP.