To fight against the pandemic of COVID-19, measures such as suspending intracity public transport, closing entertainment venues, and banning public gatherings were taken by Wu Han government to reduce case incidence[17]. Subsequently, nonpharmaceutical interventions (NPIs), such as preventing social gatherings, wearing masks, practicing hand hygiene, and delaying the spring 2020 semester in primary and middle schools, were taken to prevent the spread of SARS-CoV-2, since there were no effective measures like vaccines available worldwide [13]. These NPIs also caused the prevalent change of other respiratory viruses, especially the influenza, which was the most important viral pathogen in ARI in Shanghai[14, 15].
In this study, we analyzed the prevalence of the respiratory viruses causing the acute respiratory infections in Shanghai before, during and after COVID-19 from 2019 to 2020. There were no significant differences of the demography characteristics of ARI patients between 2019 and 2020 (Table 1) and samples of ARI-patients in this study were detected by the TaqMan low density array (TLDA) method from Jan. 2019 to Dec. 2020 though we started the surveillance of ARI in Shanghai from 2012[15], which reflected the real influences of NPIs to the prevalent of respiratory viral pathogens in ARI patients.
Since most people were asked to stay at home from 1st, March to 30th, May, in 2020, fewer samples were collected, and no positive results were obtained for the ARI cases and respiratory viral pathogens. Although it could not prove that there were no ARIs in Shanghai during that period, the measure kept the respiratory viral pathogens silence. However, the total number of ARI cases in the surveillance system was declined from 1,710 to 1,034 and the detection rate of total viral pathogens was declined from 34.5–15.2%, which were similar to the normal surveillance periods results in 2011–2015 in shanghai[14, 15], 2016–2019 in Rome[18] and 2019–2020 in Canada[19].
Our study did not find significant differences in ARI patients’ demographics between two years without changing surveillance hospitals (Table 1). However, the NPIs triggered the fall of the outpatient and inpatient visits associated with the diagnosis of ARI, the transmission routes through droplets, aerosols and physical contact of which were the same as COVID-19, in Shanghai after 1st Mar. 2020. The situation also happened in respiratory tract infections in Japan[20], Germany[21] and United States[22] during the COVID-19 pandemic.
Patients, were infected with IFVA, had clinical symptoms such as fever, chilly or rigor[23]. Generally, the clinical symptoms of RVs’ infection with ARI are mild and should always be ignored. It was surprising found that the incidence of most clinical characteristics of ARI decreased significantly in our study. Future studies should investigate whether the NPIs could relieve the symptoms of the infection.
Previous studies[24–28] showed seasonal influenza decreased in late 2020 in Europe, Canada, New Zealand, Japan and the United States. In our study, the relative change of the positive rate of IFVA were decreased significantly at Phase I and Phase II, suggesting the prevalence of IFVA seemed to be ended at the beginning of 2020. The relative change of positive rate of IFVB was increased dramatically to 7832% in Phase I, indicating the start prevalence of IFVB in Shanghai in late 2020. However, the prevalence of IFVB was prevented immediately as the NPIs and the positive rates of IFVB became zero in Phase II and Phase III, subsequently.
Studies in children about the infection of ADV showed the positive rates of ADV in 2020 were significantly lower than the levels of the same period in 2019 in Hangzhou[29], Shenzhen[30], China. Our results also showed that ADV was the main RV that infected children under 14-year besides IFV and the detection rate of ADV was much lower than that in 2020.
Previous studies showed that a prevalent peak of HPIV in children in the winter season in 2020 in Shanghai and the detection rate of PIV was higher than the same period in 2019[26]. Here, the detection rate of HIV3 was the only type of PIV that increased significantly in 15-24y and 25-59y age groups in 2020 compared with the same period and age groups in 2019. The result differed as their surveillance was one hospital surveillance and their patients were all children.
In our study, the detection rate of RSVA showed significantly decreased in 0-4y age group at the beginning of 2020, which was the same with the report of RSV detection in Australian children [31] and there was also no significant change in the winter in 2020, as the RSVA was always considered as the main cause of viral pneumonia in children [23]. We found that the increased positive rate of RSVB in medical personal group in 25-59y age group, which was also a viral pathogen in our study that the detection rate raised in that age group in Phase III in 2020 besides HPIV3.
Compared with the positive rate of HMPV in 2019, the detection rate of HMPV in children was increased in Shenzhen, China in 2020[32]. In our study, however, the positive rate of HMPV decreased significantly in children under age 5 in 2020 and in 5–14 age group, 25-59age group and older than 60 age group, (Table 3).
However, our study used the same detection methods and the distribution of patients did not change significantly, there are still several limitations and deficiencies. Firstly, the viral activity did not know as the method was based on TLDA, one kind of polymerase chain reaction (PCR), which couldn’t distinguish whether the virus was alive or not, and NPI measures couldn’t be inferred with the detection results. Secondly, the pandemic of COVID-19 might change the behavior of the patients with respiratory infection, such as drinking water instead of taking tablets, and their healthcare-seeking behavior might change in the future. Thirdly, the study period only last two years and the small number of samples in Phase II and Phase III might bring some errors and lack of some analysis. Fourthly, the NPIs lead a hard environment for the respiratory virus, which might enhance the speed of the mutant of the viruses in the near future.
It will help in designing strategies to fight against infections and outbreaks if we understand the circulation pattern and prevalence of respiratory viruses. By using NPIs to fight against the COVID-19, people changed their behavior and habits, which led to the change of transmission of other respiratory viruses.