Respiratory disease, the environment, and the military: important, unexplored frontiers.

In this issue of the Journal, Broderick et al. [1] report on the incidence of febrile respiratory illness (FRI) among Marine recruits during their first 4 weeks of military training, as well as the effect that closed training environments (units closed to the influx of potentially infectious convalescing persons [hereafter referred to as “closed units”]) versus open training environments (units open to the influx of potentially infectious convalescing persons [hereafter referred to as “open units”]) had on the transmission of respiratory pathogens, specifically adenoviruses. The open units accepted recruits transferring from medical convalescent or physical conditioning units. Up to 10% of these transferred recruits had adenoviruses identified in pharyngeal specimens. Closed units did not accept new people into their units. Broderick and colleagues also monitored FRI rates relative to the sizes of the military units, which varied from 50 to 90 men, and they collected environmental samples from living areas and medical clinics to test for adenoviruses [1]. Salient among their conclusions are that (1) high rates of FRI were likely related to the survivability and transmissibility of adenoviruses on environmental surfaces, because the intervention of social distancing (i.e., “cohorting”) did not decrease the FRI rates, and because viable adenoviruses were found in 5%–9% of environmental samples; and (2) recruit units with larger populations (i.e., units larger than the median size) had statistically significant higher FRI rates, suggesting that larger populations facilitated pathogen transmission [1]. Broderick et al. [1] studied the longstanding military recruit training center version of social distancing known as “cohorting.” Cohorting involves the establishment of military units very early in training and then the restriction of contact between members of the cohort and those outside the cohort. During the study, the Marine recruits were subjected to highly disciplined cohorting, with the open units being seeded by the introduction of new people, some of whom brought adenoviruses with them. The study by Broderick and colleagues provides support for emphasizing personal hygiene and the cleaning of environmental surfaces to control respiratory disease, but it provides no support for pursuing greater discipline in cohorting. Regarding the size of the military units, the authors’ finding that units with larger populations had higher FRI rates [1] was not unexpected. In the 1940s, a study conducted among Navy recruits by Breese et al. [2] found that the occurrence of respiratory illness was associated with the number of people assigned to a room. In contrast, another Navy study [3] reported that personnel in newer barracks, where there was more space per recruit, experienced lower FRI rates, even though the number of recruits per room did not differ between the old and the new barracks; this finding suggests that space allocation per recruit was a factor in the transmission of respiratory disease. Reported studies of the effects of reducing crowding and implementing other nonpharmaceutical interventions on the incidence of respiratory illnesses were reviewed by Lee et al. [4], who concluded that reducing crowding and using related interventions may be beneficial but deserve further evaluation. Lee et al. [4] also reported that, although population-based data on hand washing and hand antisepsis (when soap and water were not available) were limited, the studies that had been done were encouraging. Received 25 July 2008; accepted 25 July 2008; electronically published 29 September 2008. Potential conflicts of interest: none reported. The opinions or assertions contained herein are the private views of the authors, and are not to be construed as official, or as reflecting true views of the Department of the Army or the Department of Defense. Reprints and correspondence: Dr. Jose L. Sanchez, Global Emerging Infections Surveillance and Response System, Dept. of Defense Armed Forces Health Surveillance Center, 2900 Linden Ln., Ste. 103, Silver Spring, MD 20910 ([email protected]). The Journal of Infectious Diseases 2008; 198:1417–9 © 2008 by the Infectious Diseases Society of America. All rights reserved. 0022-1899/2008/19810-0001$15.00 DOI: 10.1086/592712 E D I T O R I A L C O M M E N T A R Y