Epidemiological and etiological characteristics of 1266 patients with severe acute respiratory infection in central China, 2018-2020: a retrospective survey

Abstract

Background: Severe acute respiratory infection (SARI), a significant global health concern, imposes a substantial disease burden. In China, there is inadequate data concerning the monitoring of respiratory pathogens, particularly bacteria, among patients with SARI. Therefore, this study aims to delineate the demographic, epidemiological, and aetiological characteristics of hospitalised SARI patients in Central China between 2018 and 2020.

Methods: Eligible patients with SARI admitted to the First Affiliated Hospital of Zhengzhou University between 1 January 2018 and 31 December 2020 were included in this retrospective study. Within the first 24 h of admission, respiratory (including sputum, nasal/throat swabs, bronchoalveolar lavage fluid, thoracocentesis fluid, etc.), urine, and peripheral blood specimens were collected for viral and bacterial testing. A multiplex real-time polymerase chain reaction (PCR) diagnostic approach was used to identify human influenza virus, respiratory syncytial virus, parainfluenza virus, adenovirus, human bocavirus, human coronavirus, human metapneumovirus, and rhinovirus. Bacterial cultures of respiratory specimens were performed with a particular focus on pathogenic microorganisms, including S. pneumoniae, S. aureus, K. pneumoniae, P. aeruginosa, Strep A, H. influenzae, A. baumannii, and E. coli. In cases where bacterial culture results were negative, nucleic acid extraction was performed for PCR to assay for the above-mentioned eight bacteria, as well as L. pneumophila and M. pneumoniae. Additionally, urine specimens were exclusively used to detect Legionella antigens. Furthermore, epidemiological, demographic, and clinical data were obtained from electronic medical records.

Results: The study encompassed 1266 patients, with a mean age of 54 years, among whom 61.6% (780/1266) were males, 61.4% (778/1266) were farmers, and 88.8% (1124/1266) sought medical treatment in 2020. Moreover, 80.3% (1017/1266) were housed in general wards. The most common respiratory symptoms included fever (86.8%, 1122/1266) and cough (77.8%, 986/1266). Chest imaging anomalies were detected in 62.6% (792/1266) of cases, and 58.1% (736/1266) exhibited at least one respiratory pathogen, with 28.5% (361/1266) having multiple infections. Additionally, 95.7% (1212/1266) of the patients were from Henan Province, with the highest proportion (38.3%, 486/1266) falling in the 61-80 years age bracket, predominantly (79.8%, 1010/1266) seeking medical aid in summer and autumn. Bacterial detection rate (39.0%, 495/1266) was higher than viral detection rate (36.9%, 468/1266), with the primary pathogens being influenza virus (13.8%, 175/1266), K. pneumoniae (10.0%, 127/1266), S. pneumoniae (10.0%, 127/1266), adenovirus (8.2%, 105/1266), P. aeruginosa (8.2%, 105/1266), M. pneumoniae (7.8%, 100/1266), and respiratory syncytial virus (7.7%, 98/1266). During spring and winter, there was a significant prevalence of influenza virus and human coronavirus, contrasting with the dominance of parainfluenza viruses in summer and autumn. Respiratory syncytial virus and rhinovirus exhibited higher prevalence across spring, summer, and winter. P. aeruginosa, K. pneumoniae, and M. pneumoniae were identified at similar rates throughout all seasons without distinct spikes in prevalence. However, S. pneumoniae showed a distinctive pattern with a prevalence that doubled during summer and winter. Moreover, the positive detection rates of various other viruses and bacteria were lower, displaying a comparatively erratic prevalence trend. Among patients admitted to the intensive care unit, the predominant nosocomial bacteria were K. pneumoniae (17.2%, 43/249), A. baumannii (13.6%, 34/249), and P. aeruginosa (12.4%, 31/249). Conversely, in patients from general wards, predominant pathogens included influenza virus (14.8%, 151/1017), S. pneumoniae (10.4%, 106/1017), and adenovirus (9.3%, 95/1017). Additionally, paediatric patients exhibited significantly higher positive detection rates for influenza virus (23.9%, 11/46) and M. pneumoniae (32.6%, 15/46) compared to adults and the elderly. Furthermore, adenovirus (10.0%, 67/669) and rhinovirus (6.4%, 43/669) were the primary pathogens in adults, while K. pneumoniae (11.8%, 65/551) and A. baumannii (7.1%, 39/551) prevailed among the elderly, indicating significant differences among the three age groups.

Discussion: In Central China, among patients with SARI, the prevailing viruses included influenza virus, adenovirus, and respiratory syncytial virus. Among bacteria, K. pneumoniae, S. pneumoniae, P. aeruginosa, and M. pneumoniae were frequently identified, with multiple infections being very common. Additionally, there were substantial variations in the pathogen spectrum compositions concerning wards and age groups among patients. Consequently, this study holds promise in offering insights to the government for developing strategies aimed at preventing and managing respiratory infectious diseases effectively.

Keywords: Central China; Epidemiologic characteristics; Hospitalised patients; Respiratory pathogen; Severe acute respiratory infection.

Fig. 1

Study flow chart

Fig. 2

Epidemiological characteristics of 1266 patients with severe acute respiratory infection. Geographic distribution (A) distribution of patients according to sex and age by the month of visit (B)

Fig. 3

Respiratory pathogen spectrum of 1266 patients with severe acute respiratory infection. Overall pathogen distribution (A) comparison of the number of patients with positive bacterial and viral tests (B) pathogen distribution across different years (C)

Fig. 4

Differences in the pathogen spectrum among patients in different years of visits.For each pathogen, the positive rate on the Y-axis is the number of patients who tested positive for respiratory pathogen in that year divided by the number of patients in that year

Fig. 5

Detection of respiratory viruses in patients with severe acute respiratory infection seeking medical treatment in different seasons. Each image illustrates the seasonal distribution of the pathogen. For each pathogen, the positive rate on the Y-axis is the number of patients who tested positive for respiratory viruses in that season divided by the number of patients in that season. Influenza virus (A) respiratory syncytial virus (B) parainfluenza virus (C) adenovirus (D) human bocavirus (E) human coronavirus (F) human metapneumovirus (G) rhinovirus (H)

Fig. 6

Detection of respiratory bacteria in patients with severe acute respiratory infection seeking medical treatment in different seasons. Each image illustrates the seasonal distribution of the pathogens. For each pathogen, the positive rate on the Y-axis is the number of patients who tested positive for respiratory bacteria in that season divided by the number of patients in that season. Pseudomonas aeruginosa (A) Klebsiella pneumoniae (B) Staphylococcus aureus (C) Streptococcus pneumoniae (D) Haemophilus influenzae (E) Group A haemolytic streptococcus (F) Mycoplasma pneumoniae (G) Legionella (H) Acinetobacter baumannii (I); Escherichia coli (J)

Fig. 7

Differences in respiratory pathogen spectrums between patients with severe acute respiratory infection admitted to the intensive care unit and those in general wards. The positive rate on the Y-axis is the number of patients who tested positive for respiratory pathogens divided by the total number of patients. Statistical significance in terms of the detection rate between the two groups was set at P < 0.05 (marked with an asterisk)

Fig. 8

Differences in the respiratory pathogen spectrums among patients with severe acute respiratory infection across different age groups. The positive rate on the Y-axis is the number of patients who test positive for respiratory pathogens divided by the total number of patients. Statistical significance in terms of the detection rate among the three groups was set at P < 0.05 (marked with an asterisk)