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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). Conclusion: 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.

We describe incidence and risk factors for pandemic (H1N1) 2009 virus infection in healthcare personnel during the June–September 2009 epidemic in Singapore. Personnel contributed 3 serologic samples during June–October 2009, with seroconversion defined as a >4-fold increase in hemagglutination inhibition titers to pandemic (H1N1) 2009. Of 531 participants, 35 showed evidence of seroconversion. Seroconversion rates were highest in nurses (28/290) and lowest in allied health staff (2/116). Significant risk factors on multivariate analysis were being a nurse (adjusted odds ratio [aOR] 4.5, 95% confidence interval [CI] 1.0–19.6) and working in pandemic (H1N1) 2009 isolation wards (aOR 4.5, 95% CI 1.3–15.6). Contact with pandemic (H1N1) 2009–infected colleagues (aOR 2.5, 95% CI 0.9–6.6) and larger household size (aOR 1.2, 95% CI 1.0–1.4) were of borderline significance. Our study suggests that seroconversion was associated with occupational and nonoccupational risk factors.