Viral agents responsible for febrile respiratory illnesses among military recruits training in tropical Singapore

Abstract

Background: Military personnel are highly susceptible to febrile respiratory illnesses (FRI), likely due to crowding, stress and other risk factors present in the military environment.

Objective: Our objective was to investigate the viral etiological agents responsible for FRI among military recruits training in a tropical climate in Singapore.

Study design: From March 2006 through April 2007, a total of 1354 oropharyngeal (throat) swabs were collected from military recruits who reported sick with an oral temperature of > or =38 degrees C and a cough and/or sore throat. Real-time polymerase chain reaction (PCR) was used to assay for the presence of influenza A and B viruses and adenoviruses (H-AdV), and conventional PCR used for the remaining respiratory viruses in all specimens.

Results: Influenza A virus was the dominant infection with a laboratory-confirmed incidence of 24% (326/1354) and a predominance of the H3N2 subtype. The temporal pattern for influenza A virus infections coincided with the nation-wide pattern in the civilian community. Detection rates of 12% (159/1354) and 2.7% (5/1354) were obtained for influenza B virus and other respiratory viruses, respectively.

Conclusions: The laboratory findings identified influenza A virus as the primary causative viral agent for FRI in the Singapore military, in strong contrast to findings from temperate countries and countries where recruits are often vaccinated for influenza. Our results suggest that influenza vaccination should be considered as a requirement to reduce the incidence of influenza infections. This is the first report describing respiratory infections in a tropical military setting, in a developed country in Asia.

Fig. 1

Number of FRI specimens collected showing PCR positive for the laboratory-confirmed incidence of influenza A and B viruses, and H-AdV. The real-time PCR testings were performed on the LightCycler, and the results for the presence of influenza viruses were read on the F1 channel and that for H-AdV were differentiated from non-specific products such as primer-dimers via the different melting points. The laboratory-identified incidences of FRI, measured by the total number of specimens collected, were monitored on a monthly basis together with the specific incidences of influenza viruses and H-AdV. The disease data are presented as incidence, as rate data could not be collected due to the classified nature of recruit population data. (■) represents total number of specimens collected that fulfilled the FRI criterion, () PCR positive for the presence of influenza A virus, () for influenza B virus and (□) for H-AdV.