Epidemiological and clinical characteristics of respiratory viruses in 4403 pediatric patients from multiple hospitals in Guangdong, China

Acute respiratory infection (ARI) is a common clinical disease and defining the cause is deceptively difficult [6]. Accurate and rapid identification of pathogens causing acute respiratory infection is essential for the application of appropriate antiviral therapy and the prevention of overuse of antibiotics. Although there are many reports of retrospective analyses of respiratory virus infection in Guangdong, China, few articles report comprehensive analyses from multiple hospitals. In this study, 4403 pediatric patients aged 0–18 years were recruited from 16 hospitals in 10 cities of Guangdong, China in 2019, namely Guangzhou, Zhuhai, Shenzhen, Dongguan, Huizhou, Zhanjiang, Zhongshan, Yangjiang, Jiangmen and Foshan (Additional file 1).

In our study, the detection rate of respiratory viruses in children with ARI was 24.96 %. In other studies, the rates ranged from 24.5 to 72.3 % in other regions of China and other countries [4, 5, 7‐9], which indicates the complexity and diversity of ARI etiology. RSV and IFA were the two most frequently detected viruses in this study. This result is in good agreement with some previous studies [9‐11], but differs from other studies [12, 13]. Our study indicated that RSV was the dominate cause of respiratory infection in children and the detection rate of RSV decreased with age, owing to the maturation of the immune system [14]; this finding was similar to previous reports [9, 11, 15]. IFA was the second most common respiratory virus. Influenza virus prevalence increased with age, which agreed with previous reports [8, 11], but differed from another study [9], and may be due to a greater opportunity for transmission within day care or preschool and more frequent social mixing by older children and those of school age [16]. In this study, the detection rate of ADV was the third highest, and it was more likely to infect pre-adolescents (2–12 years old) (P < 0.05); it is considered to be an important cause of respiratory tract infections in children [17]. Owing to the variability in virus transmission dynamics among humans, such as the reproductive number (R0), the rate of mutation accumulation, the duration of immunity, and the presence of cross-protection [8], the age distribution of these viruses shows diversity which may contribute to the determination of appropriate pediatric care and disease diagnosis.

ARI is frequently seasonal, particularly in regions with temperate climates [18]. In the Northern Hemisphere, respiratory viruses are reported to be more active from November to March [19]. In our study, the same trend was shown: the virus detection rate in winter (December, January, February) and spring (March, April, May) was higher than that in summer and autumn. However, in February, the detection rate of the virus was significantly lower than that of the other 2 months (December and January). A possible reason might be that the Chinese Lunar New Year occurs in February, and many people go home for the Spring Festival holiday. In addition, Guangdong Province is a large province with a floating population, and in February the population aggregation in public places decreases significantly. Infection with IFA, IFB and RSV was seasonal, with high incidence in winter and spring, consistent with findings reported in Spain, the USA [20, 21], and Shanghai, China [4], but different from Qingdao, China [18], and other counties [9, 22, 23], which suggested that there were regional differences in virus prevalence. The detection rate of ADV peaked in July 2019 (10.51 %), which was similar to what has been found in Beijing, China [24], where ADV was primarily detected in the summer; however, in Kuwait, peaks occurred in November and March [25]. In our study, many cases of PIV2 infection were detected in the autumn-winter season, while PIV3 showed clear seasonality with yearly outbreaks in the spring-summer season, consistent with a previous report [26], but PIV1 infections peaked in spring, not in autumn. Seasonal variation may correlate with viral interference [27]; China’s complex climate, including low temperature, humidity, and precipitation, and geography, as well as its diverse socio-economic and demographic characteristics, have led to different patterns of seasonal virus infections, suggesting that more studies are needed to guide vaccination times in the south of China [28].

In our study, it was shown that the most common clinical symptoms were fever and cough in children with acute respiratory infection, consistent with a previous report [29]. Our data suggested that cough was associated with RSV detection. RSV infection was more likely to be associated with lower respiratory tract infection (10.33 %) and severe pneumonia (12.5 %), as previously reported [13, 30], which indicated that it was necessary to pay more attention to RSV infection. Symptoms associated with infection of IFA were fever, shivering, nasal congestion, abdominal pain and neurological symptoms. More influenza cases had high fever at hospital admission than those without influenza [31]. This suggested that, in the influenza epidemic season, children with high fever should be first assessed for IFA infection, and need active treatment to reduce the possibility of febrile seizures. PIV1 and PIV3 were associated with absence of fever, which indicated that if there was no fever a patient may be infected with PIV1 or PIV3. However, the symptoms of respiratory virus infections are usually clinically similar, so it is very important that the detection of pathogen infection through direct or indirect fluorescence and other laboratory tests be used to provide clinicians with diagnostic evidence.

This study reflected the respiratory virus infections in pediatric patients with ARI in Guangdong, China during 2019. The large data set from 16 hospitals provided an adequate database, which allowed us to draw meaningful conclusions regarding the agents.

Regrettably, some other common respiratory viruses and bacteria were not included in our study and the pathogens detected by direct immunofluorescence antibody assay are extremely limited. Further studies should be undertaken and continuous surveillance periods should provide more information concerning the epidemiology of respiratory virus infections, the pathogenesis and interactions of co-infections and their associations with clinical outcomes.