Viral and atypical bacterial aetiologies of infection in hospitalised patients admitted with clinical suspicion of influenza in Thailand, Vietnam and Indonesia

Background Influenza constitutes a leading cause of morbidity and mortality worldwide. There is limited information about the aetiology of infection presenting clinically as influenza in hospitalised adults and children in South-East Asia. Such data are important for future management of respiratory infections. Objectives To describe the aetiology of infection presenting clinically as influenza in those hospitalised in South-East Asia. Methods Respiratory specimens archived from July 2008 to June 2009 from patients hospitalised with suspected influenza from Indonesia, Thailand and Vietnam were tested for respiratory viruses and atypical bacteria by polymerase chain reaction. Results A total of 1222 patients' samples were tested. Of 1222, 776 patients (63.5%) were under the age of 5. Viruses detected included rhinoviruses in 229 of 1222 patients (18.7%), bocaviruses in 200 (16.4%), respiratory syncytial viruses in 144 (11.8%), parainfluenza viruses in 140 (11.5%; PIV1: 32; PIV2: 12; PIV3: 71; PIV4: 25), adenovirus in 102 (8.4%), influenza viruses in 93 (7.6%; influenza A: 77; influenza B: 16) and coronaviruses in 23 (1.8%; OC43: 14; E229: 9). Bacterial pathogens were Mycoplasma pneumoniae (n = 33, 2.7%), Chlamydophila psittaci (n = 2), C. pneumoniae (n = 1), Bordetella pertussis (n = 1) and Legionella pneumophila (n = 2). Overall, in-hospital case fatality rate was 29 of 1222 (2.4%). Conclusion Respiratory viruses were the most commonly detected pathogens in patients hospitalised with a clinical suspicion of influenza. Rhinovirus was the most frequently detected virus, and M. pneumoniae, the most common atypical bacterium. The low number of detected influenza viruses demonstrates a low benefit for empirical oseltamivir therapy, unless during an influenza outbreak