Changes in Clinical Presentation and Epidemiology of Respiratory Pathogens Associated With Acute Respiratory Illness in Military Trainees After Reintroduction of Adenovirus Vaccine

Yun, Heather C.; Young, Adam N.; Caballero, Manuel Y.; Lott, Lisa; Cropper, Thomas L.; Murray, Clinton K.

Reintroduction of the Ad vaccine in basic training populations has again been extraordinarily successful in reducing the burden of both Ad-related respiratory illness and the burden of respiratory illness with fever. 75% reductions in FRI have been demonstrated by others, including at Joint Base San Antonio-Lackland where this study was conducted, against the backdrop of a 99.6% reduction in the weekly rate of Ad-related illness [11, 16] . Sustaining the commitment to prevention of Ad-related illness in uniquely susceptible trainees will be necessary if history is not to repeat itself. However, prevention of respiratory illness in this population is a complex task. Risk factors for transmission of respiratory pathogens will continue to be present in conditions inherent to basic military training. Adenovirus, despite its preeminence as a pathogen of interest in this group, has never been the entire story, and large outbreaks of non-vaccine serotype Ads have occurred even while vaccine serotypes were circulating [9] . Influenza causes annual epidemics which, in the context of an effective vaccine program, are typically limited in this population, but which can have considerable impact when new strains emerge. In summer and fall of 2009, influenza was responsible for 20% of FRI in those who were tested [20, 21] . Large outbreaks of pharyngitis caused by S. pyogenes, complicated by acute rheumatic fever, pneumonia, necrotizing skin and soft tissue infections, and other suppurative and immunologic complications, have been reported throughout the past century, prompting widespread use of antimicrobial prophylaxis at training sites [22] [23] [24] . Pneumococcal outbreaks have also occurred despite such prophylaxis, including pneumonia and fatal meningitis [25, 26] . Others, including Neisseria meningitidis, Bordetella pertussis, M. pneumoniae, and C. pneumoniae, have been well-described in this population [27] . Horizontal efforts at respiratory infection prevention, such as promoting hand hygiene, environmental including gas mask disinfection, cohorting of ill trainees, and respiratory etiquette, will require continued emphasis, even with near-elimination of Ad-related illness. However, vertical measures targeting specific organisms have also been demonstrated to have significant impact, with Ad vaccine as the prime example, and ongoing exploration into post-VI causes of illness will be necessary to direct further interventions. Furthermore, although widespread efforts exist to monitor FRI rates and conduct surveillance for common respiratory viruses, not all acute respiratory illness is febrile. Clearly, trainees are still presenting for illness, but those without fever, which now represent >90% of those presenting for care, will not have respiratory pathogen analysis via DoD-directed surveillance mechanisms. Few prior data inform clinical differences between those presenting with Ad vs other respiratory pathogens. Recent comparisons of pdm(09)H1N1 influenza and Ad, including an analysis from this cohort, corroborated a predominance of coryza and cough presentations for influenza, vs pharyngitis for Ad [20, 21] . This evaluation again emphasizes a classic presentation of Ad-related illness: fever, systemic complaints, and pharyngitis, distinct from the afebrile, coryza/ cough presentations of those presenting post-VI and with rhinovirus. Interestingly, documentation of abnormal lung examination findings increased post-VI, as did use of clini