Respiratory Pathogen Profiles of Patients - Beijing Municipality, China, November 2023-April 2024

Respiratory pathogens pose a complex challenge for public health systems. In the winter of 2023, multiple respiratory pathogens showed staggered epidemic waves. Additionally, co-infections involving various pathogens were observed, resulting in significant disease burdens. Understanding the epidemiological dynamics of these pathogens is essential for supporting public health systems in the prevention and control of respiratory infectious diseases.

Respiratory samples were collected from patients in Beijing presenting with influenza-like symptoms to detect 27 respiratory pathogens using multiplex qPCR.

Four distinct epidemic waves were identified. The first wave was a pre-winter outbreak of Mycoplasma pneumoniae (M. pneumoniae). This was then followed by successive waves of influenza A and B viruses. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) exhibited a resurgence by the end of February 2024. Age-dependent susceptibility varied, with SARS-CoV-2 and influenza A/B peaking in the 30-40-year age group. Conversely, adenovirus, rhinovirus, M. pneumoniae, Moraxella catarrhalis (M. catarrhalis), and Haemophilus influenzae (H. influenzae) were more common in adolescents and the elderly. Furthermore, 18.8% of cases were identified as co-infections with more than two pathogens. H. influenzae was found to frequently co-infect with viral and bacterial pathogens.

Respiratory pathogens exhibited different prevalence trends during the first influenza season following the COVID-19 pandemic. Influenza viruses showed a higher peak incidence and delayed seasonality. Moreover, the co-circulation of viral and bacterial infections increased the complexity of respiratory infections. Interestingly, staggered epidemic waves between SARS-CoV-2 and influenza A/B viruses were observed. Consequently, SARS-CoV-2 may become a seasonal virus, causing epidemics alongside influenza viruses. However, further research is needed to elucidate its epidemiological patterns. The co-circulation of these epidemic viruses and other respiratory pathogens underscores the need for enhanced diagnostic and intervention strategies, including vaccination campaigns.