title: Risk factors for febrile respiratory illness and mono-viral infections in a semi-closed military environment: a case-control study.
abstract: BACKGROUND
  Febrile respiratory illness (FRI) results in substantial burden in semi-closed environments. Tackling risk factors may reduce transmission and infection. However, risk factors involved in one setting may not be generalizable in all settings due to differences in climate, residential environment, population genetic and cultural backgrounds. This study aims to identify risk factors of FRI and mono-viral infections in a tropical military environment.
  
  
  METHODS
  From year 2009 to 2012, military personnel with temperature ≥37.5 °C, cough and/or sore throat, and personnel with no fever or no respiratory symptoms were recruited as cases and controls, respectively. Subjects provided nasal wash specimens and answered a standardized questionnaire. Resplex assays were used to determine the viral etiologies. Descriptive, univariate and multivariate analyses of the variables were performed using appropriate descriptive tests and logistic regression modelling, respectively, with R program.
  
  
  RESULTS
  A total of 7,743 FRI cases and 1,247 non-FRI study controls were recruited. Increasing age [adjusted odds ratio (AOR) = 1.03; 95 % confidence interval (CI) = 1.01-1.05], recruit camp (AOR = 4.67; 95 % CI = 3.99-5.46) and smoker (AOR = 1.31; 95 % CI = 1.13-1.52) were independent risk factors of FRI. Malay ethnicity was positively associated with influenza A(H1N1)pdm09 (AOR = 1.50; 95 % CI = 1.04-2.15) and coxsackie/echovirus (AOR = 1.67; 95 % CI = 1.19-2.36) mono-infection. Significant contact risk factors were stay-out personnel with ill household member (AOR = 4.96; 95 % CI = 3.39-7.24), and stay-in personnel with ill bunkmate and household member (AOR = 3.55; 95 % CI = 2.57-4.91). Staying in camp with none ill in bunk and at home was a protective factor against FRI (AOR = 0.80; 95 % CI = 0.64-0.99). These contact risk factors were similarly observed for the five most common viruses detected, namely adenovirus, rhinoviruses, influenza A and B, and coxsackie/echovirus.
  
  
  CONCLUSIONS
  Increasing age, smoker, recruit-camp, stay-out personnel with ill household members and stay-in personnel with ill bunkmates were independent risk factors of FRI in a semi-closed military environment. Early identification and isolation of ill personnel from their bunk may be effective to prevent and reduce transmission and disease burden.
authors.affiliation: Centre for Infectious Disease Epidemiology and Research, Saw Swee Hock School of Public Health, National University of Singapore, Singapore, Singapore. pangv@hotmail.com.|Communicable Disease Centre, Institute of Infectious Diseases and Epidemiology, Tan Tock Seng Hospital, Singapore, Singapore. pangv@hotmail.com.
authors.forename: Junxiong
authors.initials: J
authors.lastname: Pang
authors.affiliation: Centre for Infectious Disease Epidemiology and Research, Saw Swee Hock School of Public Health, National University of Singapore, Singapore, Singapore. jinjing82.meng@gmail.com.
authors.forename: Jing
authors.initials: J
authors.lastname: Jin
authors.affiliation: Defence Medical and Environmental Research Institute, Singapore, Singapore. jimmyloh@dso.org.sg.
authors.forename: Jin Phang
authors.initials: JP
authors.lastname: Loh
authors.affiliation: Defence Medical and Environmental Research Institute, Singapore, Singapore. tboonhua@dso.org.sg.
authors.forename: Boon Huan
authors.initials: BH
authors.lastname: Tan
authors.affiliation: Defence Medical and Environmental Research Institute, Singapore, Singapore. kweehong@dso.org.sg.
authors.forename: Wee Hong Victor
authors.initials: WH
authors.lastname: Koh
authors.affiliation: Defence Medical and Environmental Research Institute, Singapore, Singapore. ng_sock_hoon@dso.org.sg.
authors.forename: Sock Hoon
authors.initials: SH
authors.lastname: Ng
authors.affiliation: Biodefence Centre, Ministry of Defence, Singapore, Singapore. marchozj@gmail.com.
authors.forename: Zheng Jie Marc
authors.initials: ZJ
authors.lastname: Ho
authors.affiliation: Biodefence Centre, Ministry of Defence, Singapore, Singapore. gao_qiuhan@defence.gov.sg.
authors.forename: Qiuhan
authors.initials: Q
authors.lastname: Gao
authors.affiliation: Centre for Infectious Disease Epidemiology and Research, Saw Swee Hock School of Public Health, National University of Singapore, Singapore, Singapore. alex.richard.cook@gmail.com.|Yale-NUS College, National University of Singapore, Singapore, Singapore. alex.richard.cook@gmail.com.|Program in Health Services and Systems Research, Duke-NUS Graduate Medical School, Singapore, Singapore. alex.richard.cook@gmail.com.|Department of Statistics and Applied Probability, National University of Singapore, Singapore, Singapore. alex.richard.cook@gmail.com.
authors.forename: Alex R
authors.initials: AR
authors.lastname: Cook
authors.affiliation: Centre for Infectious Disease Epidemiology and Research, Saw Swee Hock School of Public Health, National University of Singapore, Singapore, Singapore. hsuliyang@gmail.com.|Department of Medicine, National University of Singapore, Singapore, Singapore. hsuliyang@gmail.com.
authors.forename: Li Yang
authors.initials: LY
authors.lastname: Hsu
authors.affiliation: Biodefence Centre, Ministry of Defence, Singapore, Singapore. vernonljm@hotmail.com.
authors.forename: Vernon J
authors.initials: VJ
authors.lastname: Lee
authors.affiliation: Centre for Infectious Disease Epidemiology and Research, Saw Swee Hock School of Public Health, National University of Singapore, Singapore, Singapore. mark.chen.ic@gmail.com.|Communicable Disease Centre, Institute of Infectious Diseases and Epidemiology, Tan Tock Seng Hospital, Singapore, Singapore. mark.chen.ic@gmail.com.
authors.forename: Mark I Cheng
authors.initials: MI
authors.lastname: Chen
mesh_terms: D000256:Adenoviridae / Q000302:isolation & purification; D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D004770:Enterovirus / Q000302:isolation & purification; D004777:Environment; D005260:Female; D006801:Humans; D009980:Influenza A virus / Q000302:isolation & purification; D009981:Influenza B virus / Q000302:isolation & purification; D007251:Influenza, Human / Q000453:epidemiology / Q000635:transmission / Q000821:virology; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D008889:Military Personnel; D012229:Rhinovirus / Q000302:isolation & purification; D012307:Risk Factors; D012846:Singapore / Q000453:epidemiology; D011795:Surveys and Questionnaires; D014777:Virus Diseases / Q000453:epidemiology* / Q000635:transmission / Q000821:virology; D055815:Young Adult