the study was conducted during april 2011march 2012 at the armed forces capital hospital , a military referral hospital in seongnam , south korea . we retrospectively reviewed all medical records with international classification of diseases , tenth revision , clinical modification codes indicating acute ltri ( pneumonia , tracheobronchitis , or bronchiolitis ) ; 622 patient records met the criteria and were reviewed . general characteristics of the study population and the military hospital , as well as the method used for classifying clinical diagnoses of acute ltri , are available in the technical appendix . nasopharyngeal swab specimens were collected from 207 ( 33.3% ) of the 622 patients with an acute ltri . within 3 days , the specimens were tested ( gclabs , yongin - si , south korea ) for 12 respiratory viruses by multiplex reverse transcription pcr ; methods are described in the technical appendix . respiratory virus infections were confirmed for 87 ( 42.0% ) patients : adenovirus ( 55 [ 63.2% ] patients ) , influenza a virus ( 26 [ 29.9% ] patients ) , influenza b virus ( 4 [ 4.6% ] patients ) , rhinovirus group a ( 3 [ 3.4% ] patients ) , and parainfluenza virus ( 2 [ 2.3% ] patients ) . for all confirmed cases of viral infection , we performed an epidemiologic analysis and analyzed the clinical manifestations and prognosis for the hospitalized patients . the clinical diagnoses for acute viral ltri cases included 58 cases of pneumonia , 25 cases of tracheobronchitis , and 4 cases of bronchiolitis . pneumonia was most commonly caused by adenovirus ( 46 [ 79.3% ] cases ) ( table 1 ) . tracheobronchitis was most commonly caused by influenza a virus and adenovirus ( 14 [ 56.0% ] and 9 [ 36.0% ] cases , respectively ) . two cases each of influenza a virus infection and parainfluenza virus infection were noted among the 4 patients with bronchiolitis . the monthly distribution of the identified viruses is shown in the online technical appendix figure . * a total of 207 nasopharyngeal swab specimens were collected from soldiers with acute lower respiratory infections . within 3 days of collection , the specimens were tested against 12 respiratory viruses at gclabs ( yongin - si , south korea ) by using seeplex rv12 ace detection ( seegene , seoul , south korea ) . of the 87 patients with an ltri , 64 were hospitalized . among these 64 patients , 49 ( 76.6% ) had adenovirus infections , 13 ( 20.3% ) had influenza a or b virus infections , and 2 had bronchiolitis caused by parainfluenza virus infection . table 2 shows the clinical features of the 62 patients hospitalized for adenovirus or influenza a or b virus infection , among whom the mean age was 19.6  1.1 years ( adenovirus patients ) and 20.1  2.0 years ( influenza patients ) . except for a female patient infected with influenza a virus , the proportion of new military recruits was significantly higher among patients with adenovirus infection than among patients with influenza a or b virus infection ( p = 0.011 ) . there was no difference in the clinical signs and symptoms and radiographic findings of patients infected with influenza virus and adenovirus ( technical appendix ) . mechanical ventilation was required for 6 patients in whom severe pneumonia developed ; all 6 patients had adenovirus infection and 3 died ( technical appendix ) . the statistical analyses used in this study are described in the online technical appendix ( wwwnc.cdc.gov/eid/article/20/5/13-1692-techapp1.pdf ) . among the 17 hospitalized active - duty soldiers with adenovirus infection , those ranked as privates were the most common ( 11/17 [ 64.7% ] ) . all privates who were found to have adenovirus infection had been relocated to advanced training sites after graduating from the 6-week basic military training course , which suggests that adenovirus might have spread to secondary training sites through recruit redeployment . among the viruses identified as causing acute ltri in south korean soldiers , adenovirus was the most common , causing 63.2% of the cases . these findings are similar to those in studies among us military ( 14 ) . however , the infection was also confirmed in all 11 ( 64.7% ) privates among the 17 active duty soldiers at advanced training sites ( table 2 ) . in the south korea military , adenovirus might have spread to secondary training sites through recruit redeployment , similar to the experience in the us military ( 14 ) . cases of severe pneumonia requiring mechanical ventilation were not observed among patients with influenza virus infection ; however , 3 of the 6 patients with severe adenovirus - associated pneumonia died . this finding indicates that adenovirus infection is a major cause of death among soldiers with severe respiratory diseases . in 2009 , in response to the influenza a(h1n1)pdm09 pandemic , multiplex reverse transcription pcr for respiratory viruses became available in south korea military hospitals . before 2009 , apart from research purposes , clinical testing for respiratory viruses was not routinely performed at military hospitals . for this reason , south korea military physicians were unaware that adenovirus was a major cause of respiratory disease among soldiers . because of the lack of an effective treatment for adenovirus infection , vaccination against adenovirus has been introduced for persons , such as military recruits , at high risk for infection . first , we were unable to confirm the serotype of adenovirus for positive case - patients . because military physicians were unaware that adenovirus was a major cause of acute respiratory disease , additional serotyping was not performed at the time of diagnosis . the level of an epidemic varies at different times , thus requiring longer study periods to observe patterns . third , we retrospectively reviewed medical records of patients with acute ltri in a central referral military hospital ; thus , the study patients may not be entirely representative of south korea soldiers with acute ltri . last , there was a sampling bias with regard to the molecular assay ; the test may have been performed only in cases of severe illness or when recommended by clinicians . nevertheless , our results suggest that among south korea soldiers with acute ltris , those with adenovirus rather than other respiratory infections had more severe clinical outcomes . further studies are required to determine the serotype(s ) of adenovirus causing infection among the military , and epidemiologic surveillance for adenovirus is needed . methods and results for a study of acute lower respiratory tract infections in soldiers , south korea , april 2011march 2012.this originally said ( 11/49 [ 22.4% ] ) but was changed to reflect the number of privates among the active - duty soldiers rather than the number among the total number of soldiers hospitalized with adenovirus infection .
during april 2011march 2012 , we retrospectively reviewed medical records for south korea soldiers to assess the etiology and epidemiology of acute viral lower respiratory tract infections . 
 adenovirus was the most commonly identified virus ( 63.2% ) and the most common cause of pneumonia ( 79.3% ) and hospitalization ( 76.6% ) ; 3 soldiers died of adenovirus - related illness .