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Open Access Research article

Respiratory viral pathogens among Singapore military servicemen 2009 – 2012: epidemiology and clinical characteristics

Xin Quan Tan12, Xiahong Zhao3, Vernon J Lee13*, Jin Phang Loh4, Boon Huan Tan4, Wee Hong Victor Koh4, Sock Hoon Ng4, Mark I-Cheng Chen35 and Alex Richard Cook3678

Author Affiliations

1 Biodefence Centre, Ministry of Defence, Singapore, Singapore

2 Preventive Medicine Residency Programme, National University Health System, Singapore, Singapore

3 Saw Swee Hock School of Public Health, National University of Singapore, Singapore, Singapore

4 Defence Medical and Environmental Research Institute, Singapore, Singapore

5 Department of Clinical Epidemiology, Tan Tock Seng Hospital, Singapore, Singapore

6 Yale-NUS College, National University of Singapore, Singapore, Singapore

7 Program in Health Services and Systems Research, Duke-NUS Graduate Medical School, Singapore, Singapore

8 Department of Statistics and Applied Probability, National University of Singapore, Singapore, Singapore

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BMC Infectious Diseases 2014, 14:204  doi:10.1186/1471-2334-14-204

Published: 15 April 2014

Abstract

Background

Few studies have comprehensively described tropical respiratory disease surveillance in military populations. There is also a lack of studies comparing clinical characteristics of the non-influenza pathogens with influenza and amongst themselves.

Methods

From May 2009 through October 2012, 7733 consenting cases of febrile respiratory illness (FRI) (temperature [greater than or equal to]37.5degreesC with cough or sorethroat) and controls in the Singapore military had clinical data and nasal washes collected prospectively. Nasal washes underwent multiplex PCR, and the analysis was limited to viral mono-infections.

Results

49% of cases tested positive for at least one virus, of whom 10% had multiple infections. 53% of the FRI cases fulfilled the definition of influenza-like illness (ILI), of whom 52% were positive for at least one virus. The most frequent etiologies for mono-infections among FRI cases were Influenza A(H1N1)pdm09 (13%), Influenza B (13%) and coxsackevirus (9%). The sensitivity, specificity, positive predictive value and negative predictive value of ILI for influenza among FRI cases were 72%, 48%, 40% and 69% respectively. On logistic regression, there were marked differences in the prevalence of different symptoms and signs between viruses with fever more prevalent amongst influenza and adenovirus infections than other viruses.

Conclusion

There are multiple viral etiologies for FRI and ILI with differing clinical symptoms in the Singapore military. Influenza and coxsackevirus were the most common etiology for FRI, while influenza and adenoviruses displayed the most febrile symptoms. Further studies should explore these differences and possible interventions.

Keywords:
Influenza like-illness-ILI; Surveillance; Epidemiology; Influenza; Respiratory infections; Respiratory viruses