key: cord-0748926-g7v9gem6 authors: Yang, Qi; Xiao, Xia; Gu, Xinxia; Liang, Dong; Cao, Ting; Mou, Jun; Huang, Chunxu; Chen, Lei; Liu, Jie title: Surveillance of common respiratory infections during COVID-19 pandemic demonstrates preventive effectiveness of non-pharmaceutical interventions date: 2021-02-11 journal: Int J Infect Dis DOI: 10.1016/j.ijid.2021.02.027 sha: 18a38e8f90fd5f5740bfd00777fd02ba4a06990d doc_id: 748926 cord_uid: g7v9gem6 Objective Following the emergence of a novel coronavirus, SARS-CoV-2, and its spread outside of Wuhan, China, the human society has experienced a pandemic of coronavirus disease 2019 (COVID-19). While the development of vaccine and pharmaceutical treatment has been undergoing, government authorities in China implemented unprecedented non-pharmaceutical interventions as primary barriers to curb the spread of the deadly SARS-CoV-2. Although the decline of COVID-19 cases coincided with this implementation of interventions, we looked for evidence to demonstrate the efficacy of these interventions, since artifactual factors, such as the environment, the pathogen itself, and the phases of epidemic, may also alter the pattern of case development. Methods We surveyed common viral respiratory infections that have a similar pattern of transmission, tropism, and clinical manifestation as COVID-19 under such interventions during this season with pandemic, and compared it with historical data in previous seasons without the interventions. Results Our survey shows that the rates for common respiratory infections, such as influenza and respiratory syncytial virus infections, decreased dramatically from previous annual 13.7% (95% CI, 10.82-16.58) and 4.64% (95% CI, 2.88-7.64) to 0.73% (95% CI, 0.02-1.44) and 0.0%, respectively, in this season. Conclusions Our surveillance provides compelling evidence that the interventions are cost-effective ways to curb the spread of contagious agents, and may be the only practical approach to limiting the evolving of epidemic until vaccine and pharmaceutical treatment are available. Following the outbreak of novel severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) -induced disease, COVID-19, and its spread out of Wuhan, China, in December 2019, China experienced a public health emergency with over 83 thousand confirmed cases and 4634 deaths as of June, 2020 (Rai et al., 2020 ) . Although there are a few newly developed vaccines and treatments, it is conceivable that without some impact on transmission, the virus will continue to circulate, infect, and cause serious disease in certain segments of the unvaccinated population,since the variants of SARS-CoV-2 keep evolving, and majority of the population are going to be vaccinated. A variety of non-pharmaceutic public health interventions have been employed to cope with the emergency of this deadly pathogen and to halt the surge of COVID-19 cases. These interventions include personal and environmental hygiene, social distancing, travel restrictions, quarantine, and case isolation. The aim of these interventions is to reduce the reproduction number ( The decline in COVID-19 cases suggests that the implementation of these interventions is potentially effective. European countries like the UK have implemented measures that include national lockdowns, border closures, school closures, and international travel bans, which have reduced disease transmission and delayed the epidemic (Flaxman et al., 2020; De Lusignan et al., 2020; Jarvis et al., 2020) . Although the spatial spread of infectious diseases has been intensively studied, the effectiveness of non-pharmaceutical interventions in preventing the spread of infections is uncertain. Wuhan's travel ban was associated with a delayed arrival of COVID-19 in other cities by an estimated 2.91 days, and cities that implemented preemptive control measures reported fewer cases (Tian et al., 2020) ; Cities that suspended intra-city public transport, closed entertainment venues, and banned public gathering had fewer cases during the first week of the outbreak (Tian et al.,2020) . These observations suggested that the interventions were strongly associated with, although not necessarily the cause of, a delay in epidemic growth and a reduction in case numbers during peak COVID-19 epidemic in China . Artifactual factors, such as the environment, the pathogen itself, and the phases of epidemic, might also alter the pattern of the epidemic (Pica et al., 2012; Tang, 2009 (Chan et al., 2020; Liu et al., 2020) . The impact of these interventions on influenza and RSV-induced acute respiratory infections during COVID-19 pandemic can be a surrogate to evaluating their efficacy on SARS-CoV-2 transmission (Ferretti et al., 2020; Cowling et al., 2020) . Population density has an impact on pathogen transmissions. There was a substantial geographical variability in the prevalence of COVID-19, with higher number of reported cases around densely populated city center and lower in less populated coastal areas (Pollán et al., 2020) . High population density catalyzed the spread of COVID-19 and had great impact on the R0, as it increased contact rates (Rocklöv et al., 2020) . One of the key predictions is that the size of the epidemic increases strongly (and in a nonlinear way) with the initial density of susceptible population . Chengdu is the capital city of Sichuan province located in the south-western China with a population of 87.25 million, and is relatively distanced from the epicenter of COVID-19. The greater Chengdu area (including Chengdu and its nearby cities) is one of the most densely populated areas in China, with some areas even overcrowding. The local life style, such as social gathering and entertaining in closed-space of tea-houses and Mahjong-houses, can easily accelerate pathogen transmission. In addition, a typical subtropical climate gives Chengdu a unique pattern of transmission for respiratory pathogens (Feng et al., 2012) . During the early phase of the pandemic, the number of COVID-19 cases rose quickly but decreased dramatically with the implementation of interventions. Nevertheless, there were only 143 confirmed cases and 3 deaths until February 29th, 2020 (Si et al., 2020) . The specimens were inactivated in a water bath at 56 °C for 30 min, and the Statistical method SPSS 21.0 was used to analyze 95% confidence interval of pathogen prevalence, and the Chi-square test and Fisher exact test was used for comparison between groups. The test level was α=0.05, and P<0.05 was considered statistically significant. for IVA (2.96%, all H1N1) and SARS-CoV-2 (1.96%); groups ≥65 was positive for IVA (2.96%, including H1N1 0.97% and H3N2 0.97%) and SARS-CoV-2 (0.97%). All groups were positive for SARS-CoV-2 but the types of influenza were slightly different, except in group <18.There was no statistical difference in infection rates among age groups above 18 years (χ2=1.994, P>0.05). Our specimen pool consisted of 297 samples from male and 249 from female patients. We found both had similar positive rates for viral pathogens (4.04% male, 95% CI: 1.81-6.27; 4.02% female, 95% CI: 1.59-6.45; χ 2 =0.000, P>0.05). Among those infected, males had more diversity in pathogens than females, including 33.33% IVA (25.00% H1N1 and 8.33% H3N2), 41.67% IVB, and 25.00% SARS-CoV-2, while female had 30.00% IVB and 70.00% SARS-CoV-2 ( Figure 3 ).There were no significant differences among pathogens detected in male and female patients respectively (male, χ2=0.507, P>0.05; female, χ2=1.633, P>0.05). Our survey suggests that contraction and transmission of pathogens is highly associated with social activity. People at age 18-44 are the most active socially, with the most work-load and family duties, and thus had a higher infection rate than did other groups. People in pre-and school age had restricted social activity because of school closures, stay-home orders, and online learning; Seniors had reduced social activity due to limited public transportation, and the stress of underlying health conditions. This is in line with other reports that people with higher social contact rates are more likely to contract infections (Mossong et al., 2008) . Males and females showed no difference in rates of viral infections in our survey and other reports (Pollán et al., 2020; Huang et al., 2020) . However, males may have more social activity and personal contacts, and show more diversity in pathogens infected compared to females. The male patients had been equally positive for infections of IVA (including both H1N1, N3N2), IVB, and SARS-CoV-2, whereas female patients had only been positive for IVB and SARS-CoV-2. Thus, social distancing is one of the key measures to reduce pathogen transmission. Herd immunity is a strategy commonly used to halt pathogen transmission at its early phase and to provide protection to individuals, such as infants and seniors, who respond poorly to immunization or cannot receive vaccine inoculation for various reasons. Herd immunity can be reached when about 70-90% of a population becomes immune to a pathogen either through infection and recovery or vaccination. When herd immunity is reached, the pathogen is less likely to spread to naïve people who are not immune because there just are not enough carries or hosts for replication. But, with such high mortality, herd immunity against the SARS-CoV-2 cannot be reasonably anticipated without significant number of deaths, if the herd immunity can be established. In the case of influenza, we did not observe significant herd immunity. Our data show that IVA and IVB had almost the same prevalence as SARS-CoV-2 under the same non-pharmaceutical interventions although both types of influenza are seasonal and circulate annually, and there are vaccines available. Prior to being proven effective, relying on establishment of herd immunity through massive infections could be risky. It is still unclear whether COVID-19 survivors have immunity, and a third of infections determined by serology were reported to be asymptomatic (Pica et al., 2012) , where 40% of asymptomatic and 13% symptomatic patients had an undetectable level of antibodies 8 weeks after recovery (Long et al., 2020) . Therefore, keeping up with non-pharmaceutical interventions is necessary until a vaccine and specific treatments become available, or herd immunity is proven effective. Our study has several limitations. Under the stress of the pandemic, patients might self-medicate at home, thus decreasing the overall number of outpatient and emergency visits. But those visiting the hospital were more likely to be severely affected patients. Additionally, we only surveyed a small portion of viral respiratory infections, like IVA (including H1N1 and H3N2 subtype), IVB, RSV, and SARS-CoV-2 infection. Prevalence of other common respiratory infections, not only viral but also bacterial, need to be estimated to have a full spectrum of common respiratory infections under the implementation of non-pharmaceutical intervention. Also, assays used for historical data and this survey are slightly different although the procedure for sample collection is standardized. This may have some impact on comparison of our survey to previous data although we believe our isothermal amplification chip assay for viral pathogens are more sensitive than assays used before. In conclusion, non-pharmaceutical interventions are cost-effective approach to curb the spread of contagious agents, and may be the only practical approach to limiting the evolving epidemic of infections until vaccines and pharmaceutical treatments are widely available. ☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Table 3 Prevalence of viral respiratory pathogens in gender groups J o u r n a l P r e -p r o o f Influenza monitoring in a sentinel hospital of Chengdu city from 2011 to 2013. J of Tro Dis and Paras A familial cluster of pneumonia associated with the 2019 novel coronavirus indicating person-to-person transmission: a study of a family cluster Maternal antibodies against influenza in cord blood and protection against laboratory-confirmed influenza in infants Risk factors for SARS-CoV-2 among patients in the Oxford Royal College of General Practitioners Research and Surveillance Centre primary care network: a cross-sectional study Influenza-associated mortality in temperate and subtropical Chinese cities Quantifying SARS-CoV-2 transmission suggests epidemic control with digital contact tracing Estimating the effects of non-pharmaceutical interventions on COVID-19 in A systematic review of antibody mediated immunity to coronaviruses: antibody kinetics, correlates of protection, and association of antibody responses with severity of disease Quantifying the impact of physical distance measures on the transmission of COVID-19 in the UK Early Transmission Dynamics in Wuhan, China, of Novel Coronavirus-Infected Pneumonia Viral dynamics in mild and severe cases of COVID-19 Respiratory infections during SARS outbreak Clinical and immunological assessment of asymptomatic SARS-CoV-2 infections Social contacts and mixing patterns relevant to the spread of infectious diseases Viral infections of fever respiratory syndrome patients in Chengdu Environmental factors affecting the transmission of respiratory viruses Prevalence of SARS-CoV-2 in Spain (ENE-COVID): a nationwide, population-based seroepidemiological study Consequences of chemical impact of disinfectants: safe preventive measures against COVID-19 High population densities catalyse the spread of COVID-19 Effect of population density on epidemics Epidemiological surveillance of common respiratory viruses in patients with suspected COVID-19 in Southwest China The effect of environmental parameters on the survival of airborne infectious agents An investigation of transmission control measures during the first 50 days of the COVID-19 epidemic in China Results of influenza surveillance in Mianyang City from A comparative analysis of clinical characteristics with different subtypes of influenza confirmed at a surveillance outpost hospital in Chengdu from Analysis of influenza surveillance in sichuan from Surveillance of influenza-like illness in Chengdu City in 2015 and its evaluation Temporal patterns of influenza A subtypes and B lineages across age in a subtropical city, during pre-pandemic, pandemic, and post-pandemic seasons Research, West China Hospital, West China School of Medicine, Sichuan University for their invaluable contribution to this study.