title: Emergence of norovirus GI.2 outbreaks in military camps in Singapore.
abstract: BACKGROUND
  Simultaneous acute gastroenteritis (AGE) outbreaks occurred at two military camps. This study details the epidemiological findings, explores possible origins, and discusses preventive measures.
  
  
  METHODS
  Investigations included attack rate surveys, symptom surveys, hygiene inspections, and the testing of water, food, and stool samples. DNA/RNA was extracted from stool samples and amplified via real-time reverse transcription PCR (RT-PCR). Partial and full-length capsid nucleotide sequences were obtained, phylogenetic relationships inferred, and homology modelling of antigenic sites performed.
  
  
  RESULTS
  The military outbreaks involved 775 persons and were preceded by two AGE outbreaks at restaurants in the local community. The outbreak was longer and larger in the bigger camp (21 days, attack rate 15.0%) than the smaller camp (6 days, attack rate 8.3%). Of 198 stool samples, norovirus GI.2 was detected in 32.5% (larger camp) and 28.6% (smaller camp). These were essentially identical to preceding community outbreaks. Antigenic site homology modelling also showed differences between identified and more common AGE outbreak strains (norovirus GII.4).
  
  
  CONCLUSIONS
  Differences observed highlight difficulties in controlling person-to-person outbreaks among large groups in close proximity (e.g., military trainees). Distinct differences in antigenic sites may have contributed to increased immunological susceptibility of the soldiers to infection.
authors.affiliation: HQ Medical Corps, Singapore Armed Forces, 701 Transit Road #04-01, Singapore 778910; Ministry of Health, Singapore. Electronic address: marchozj@gmail.com.
authors.forename: Zheng Jie Marc
authors.initials: ZJ
authors.lastname: Ho
authors.affiliation: Bioinformatics Institute, A*STAR Singapore, Singapore.
authors.forename: Gunalan
authors.initials: G
authors.lastname: Vithia
authors.affiliation: DSO National Laboratories, Singapore.
authors.forename: Ching Ging
authors.initials: CG
authors.lastname: Ng
authors.affiliation: Bioinformatics Institute, A*STAR Singapore, Singapore; School of Biological Sciences, Nanyang Technological University, Singapore; National Public Health Laboratory, College of Medicine, Singapore.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Maurer-Stroh
authors.affiliation: HQ Medical Corps, Singapore Armed Forces, 701 Transit Road #04-01, Singapore 778910.
authors.forename: Clive M
authors.initials: CM
authors.lastname: Tan
authors.affiliation: DSO National Laboratories, Singapore.
authors.forename: Jimmy
authors.initials: J
authors.lastname: Loh
authors.affiliation: National Public Health Laboratory, College of Medicine, Singapore.
authors.forename: Tzer Pin Raymond
authors.initials: TP
authors.lastname: Lin
authors.affiliation: HQ Medical Corps, Singapore Armed Forces, 701 Transit Road #04-01, Singapore 778910; Ministry of Health, Singapore.
authors.forename: Jian Ming Vernon
authors.initials: JM
authors.lastname: Lee
mesh_terms: D017250:Caliciviridae Infections / Q000453:epidemiology* / Q000517:prevention & control / Q000821:virology; D036022:Capsid Proteins / Q000737:chemistry / Q000276:immunology; D004196:Disease Outbreaks; D005759:Gastroenteritis / Q000453:epidemiology* / Q000517:prevention & control / Q000821:virology; D006801:Humans; D008889:Military Personnel; D029322:Norovirus / Q000145:classification / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification; D010802:Phylogeny; D012846:Singapore / Q000453:epidemiology
chemical_list: D036022:Capsid Proteins
keywords: Disease outbreaks; Epidemiology; Military personnel; Norovirus