Study On Pathogen Spectrum Of Acute Respiratory Tract Infection In Hunan Province

Acute respiratory infection is the human most common infectious disease, and is also the main reason for death in infants. Bacteria and fungi can cause acute respiratory infection, but most of which is caused by viruses. Bacterial and fungal infections are usually subsequent to viral infection. Both mutants of traditional viruses and the novel viruses, such as human metapneumovirus (HMPV), new subtypes of coronavirus and bocavirus (HBoV), have further expanded the pathogenic spectrums of the respiratory infection.Sentinel surveillances of Influenza-Like Illness (ILI), Severe Acute Respiratory Illness (SARI), and Febrile respiratory syndrome (FRS) are important observation systems in our country. Our study was undertaken to explore the etiology characters of patients from the three monitoring system by rapid detection kit for multiple respiratory virus. The viral profiles associated with the three observation systems in Changsha were obtained. Besides, the viral etiology of acute respiratory tract infection among pediatric inpatients and outpatients were compared. These data will provide theoretical basis for monitoring and control of the flu and other respiratory diseases.Methods:1429specimens of respiratory infections were collected from patients presenting with ILI, SARI and FRS in Hunan province during January,2011and August,2012. The nucleic acids of the specimens were extracted and analyzed by Multiplex PCR Diagnostic Kit for16Respiratory Virus Types/Subtypes (ABT). Capillary electrophoresis was used as the detection platform for the virus. Then, the pathogenic spectrums of ILI, SARI and FRS, as well as the epidemiologic features such as season, age, and gender distribution of respiratory viruses were determined. At last, the etiology characters were compared between outpatient and hospitalized children. Results:Of the917patients presenting with ILI, at least one respiratory virus was identified in328(35.8%) patients. Overall, influenza virus (Flu) was the most commonly detected virus (12.0%of specimens), followed by human rhinovirus (HRV,11.2%), adenovirus (ADV,5.8%) and respiratory syncytial virus A (RSVA,4.8%). The highest detection rate was found among children<5years of age. HRV, ADV and RSVA were most common among children group. Coinfections were found in24of328positive specimens (7.3%), and most (75.0%) were in children<5years of age. While influenza virus and RSV had a defined period of circulation, the other viruses were detected throughout the year.Viral pathogen was detected in124(47.9%) patients with SARI, of which,91.9%had single-virus infections. The most common viruses were RSV (16.9%), Flu (16.2%), HRV (6.2%), ADV (4.6%) and Parainfluenza3(PIV3,3.9%). RSV was the dominant virus detected in children (<5years old) and in adolescents (6-10years old), whereas Flu was the most commonly detected virus among the middle-aged and elderly groups.RSV showed seasonal patterns. Flu had the highest detection rate in winter, and in summer and autumn, FluA and FluB circulated alternately.Among the253tested FRS specimens,155were tested positive for viral infections, resulting in a positive rate of61.3%. RSVA(23.3%)was the dominant pathogen detected, followed by HRV(13%), ADV(12.3%),PIV3(11.9%) and HBoV(7.1%).In addition, there were also10strains of HMPV (4.0%) detected. The results showed that41(16.2%) specimens were positive for two or more viruses. HRV (20/41) was the most frequently detected viral agent among co-infection specimens, followed by RSVA and PIV3. HBoV was detected in18children. A large proportion of the cases (72.2%) were mixed infections with other viruses. Viral pathogens were identified in specimens of33(76.7%) severe pneumonia cases, among which ADV was detected in20(46.5%) patients.In children group, we found that at least one viral pathogen was identified in each of153out of241inpatients and the overall positive rate was63.5%, which was significantly higher than that in outpatient(49.3%). The frequencies of detection of various viruses among in-and outpatients were different. The positive rate for RSVA, PIV3, HBoV and HMPV was significantly higher among hospitalized children than that of those viruses in the outpatient group. In addition, coinfection was more frequent in inpatients than in outpatients.Conclusions:Influenza viruses were the most commonly detected viral organisms among patients with ILL Our results demonstrate that a wide range of respiratory viral pathogens are circulating in Changsha city. Among patients with SARI, RSV and influenza virus are the most likely viral causes. Infection with respiratory viruses is an important cause of febrile respiratory syndrome. RSVA, HRV and ADV were the main pathogens leading to the fever respiratory infections in Changsha. Coinfections were common. In children group, the pathogenic profile was different between inpatients and outpatients. RSV, PIV3, HMPV and HBoV may increase the risk for hospitalization. Viral coinfections are frequently identified in hospitalized patients.