Building-Associated Risk of Febrile Acute Respiratory Disease-Reply

In Reply.— The letters of Drs Lipinski and Hodgson emphasize the point that many characteristics of indoor air are modified by mechanical ventilation systems. They suggest several specific components of indoor air as potential determinants of the health effects observed in our study. Since our report was based on routinely gathered surveillance data, we do not have information regarding the physical characteristics of the air inside the modern or old barracks during the study period. We recognize the practical significance of defining relationships of specific physical characteristics of indoor air with infectious and other health risks. In this regard, the letters emphasize an important point: since many characteristics of indoor air are affected by mechanical ventilation, studies of the health effects of specific components of indoor air must account for the potentially confounding effects of physical characteristics that concurrently vary. Until such technically difficult studies are done, however, attempts to