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• Nasopharyngeal swab is most suitable for respiratory virus surveillance. • Flu prevalence was high in 2009 and afterwards remained at a low level. • RSV epidemic was notably high in 2014 and became the most predominant virus in 2014–2018. • A high prevalence of HCoV, RSV and HBoV may be related to new strains introduction. Acute respiratory infections (ARIs) remain a significant public threat with high morbidity and mortality worldwide; viruses are significant pathogens that cause ARIs. This study was conducted to better understand the epidemiological characteristics of respiratory viruses circulating in southern China. We collected 22,680 respiratory samples from ARI patients in 18 hospitals in southern China during 2009–2018; seven common respiratory viruses including Flu, RSV, PIV, hMPV, ADV, HCoV, and HBoV were screened using in-house real-time PCR. Of all samples, 9760 ARI cases (9760/22680, 43.03%) tested positive for the seven common respiratory viruses. The most detected virus was Flu (14.15%), followed by RSV (10.33%) and PIV (5.43%); Flu-A, PIV3, and HCoV-OC43 were the predominant subtypes. Although most of the viruses were detected in male inpatients, Flu was more likely detected in female outpatients. Flu infection was more likely to cause URTI (upper respiratory tract infection), whereas RSV infection was more likely to cause pneumonia and bronchitis. The prevalence of Flu was particularly high in 2009. The epidemic level was found notably high in 2014–2018 for RSV, in 2016–2018 for PIV, in the summer of 2018 for ADV, in the summer of 2016 and winter of 2018 for HCoV, and in the summer of 2011 and autumn of 2018 for HBoV. The co-detection rate of the seven viruses was 4.70%; RSV, PIV, and Flu were the most commonly co-detected viruses. This work demonstrates the epidemiological characteristics of seven common respiratory viruses in ARI patients in southern China. [ABSTRACT FROM AUTHOR]

• For respiratory syncytial virus (RSV), an annual distribution pattern of 2-year RSV-A dominance followed by a 1-year RSV-B dominance was found in Guangzhou. • In 2011–2016 in south China, prevalent RSV-A genotypes were NA1 and ON1 and the prevalent RSV-B genotype was BA9. • The prevalent RSV-A genotype changed from Chongqing NA1 in 2011 to Hong Kong ON1 in 2014. • The highest RSV epidemic peak occurred in 2015, indicating a possible biennial peak. • The ongoing evolution of RSV-A ON1 and NA1 genotypes indicated high selection pressure. Human respiratory syncytial virus (RSV) is one of the most important pathogens that cause acute respiratory infections in children and immunocompromised adults. This work was conducted to understand the epidemiological and phylogenetic features of RSV in southern China during 2011–2016. A total of 16 024 nasopharyngeal swabs were collected from patients with respiratory infections in 14 hospitals, and screened for RSV and seven other respiratory viruses using real-time PCR. Six hundred and twenty-three RSV-positive samples from 13 hospitals were further analyzed for subtypes. G gene sequencing and phylogenetic analysis were performed based on 46 RSV-A and 15 RSV-B strains. RSV was detected in 9.5% of the 16 024 specimens, the highest among the eight respiratory viruses screened. Most of these specimens came from inpatients and children under 3 years of age. The incidence of RSV-A (9.4%) was higher than that of RSV-B (4.4%) in children (<15 years), but not in adults (0.64% vs. 0.58%). A 2-year RSV-A dominance followed by a 1-year RSV-B dominance pattern was found. The co-detection rate of RSV was 25.1%. The main prevalent genotypes were NA1, ON1, and BA9. The prevalent RSV-A genotype in 2011–2012 was NA1, close to Chongqing and Brazil, but a new Hong Kong ON1 genotype was introduced and became the prevalent genotype in Guangzhou in 2014–2015. Deduced amino acid sequence analysis confirmed the ongoing evolution and a high selection pressure of RSV-A and B strains, especially in RSV-A ON1 and NA1 genotypes. This study demonstrated the molecular epidemiological characteristics of RSV in patients with respiratory infections in southern China. [ABSTRACT FROM AUTHOR]