A novel coronavirus disease (COVID-19), caused by Coronavirus type 2 (SARS-CoV-2) emerged in Wuhan, China in December 2019, has become the third coronavirus in the past 20 years since the outbreak of severe acute respiratory syndrome coronavirus (SARS-CoV) in 2002 and the Middle East outbreak of respiratory syndrome coronavirus (MERS-CoV) in 2012. With rapidly spread all over the world and concomitant mortality burden, the COVID-19 outbreak represents a global public health issue which unseen in the last century (1–4). So far, the world has been witnessed four waves of viruses: Alpha variant (B.1.1.7), Beta variant (B.1.351), Gamma variant (P.1) and Delta variant (B.1.617.2). However, the new strain, Omicron (B.1.1.529), was discovered for the first time in South Africa in November 2021 (5). This strain has the characteristics of fast transmission, strong infectivity, high pathogenicity and short incubation period (6). Therefore, we need more rapid and immediate responses in healthcare to avoid more infections.

In December 2021, a case of localized Omicron variant occurred in Xi'an, Shaanxi. There were 2,080 new cases of coronavirus pneumonia confirmed within 40 days, the largest local outbreak in a megacity since the Wuhan outbreak (7). According to the COVID-19 Diagnostic Guide issued by China and related research, a positive real-time reverse transcription polymerase chain reaction (RT-PCR) test is considered the main criterion for the diagnosis of COVID-19 (8, 9). Nucleic acid collectors are one of the important pillars during the pandemic and play a key role during the pandemic.

In order to prevent the further spread of the epidemic, the medical institutions actively arranged nucleic acid collection teams to carry out wide range nucleic acid sampling throughout the city and closed-loop management for nucleic acid collection employees in accordance with the local epidemic prevention and control procedures. Closed-loop management is a management method formed by integrated information system, closed-loop system, management control and management closure principle. It can be effectively used in epidemic prevention and control (10). Point-to-point management allowed for closed-loop hospital locations, closed-loop roadways, closed-loop lodging sites, closed-loop epidemics and closed-loop patient status (hospital to hotel accommodation sites, hospital to quarantine sites).

During the sampling period, due to the large population of Xi'an, the sampling workload is extremely heavy, and the maximum sample size can reach 8.92 million people per day. The nucleic acid collectors need to start the preparation work at 3 am every day. The sampling site conditions are rudimentary, most of them are mobile sampling points which are temporarily constructed outdoors. And the weather is cold during the epidemic, the protective suits are too thin to keep warm. The working hours are also uncertain, most people work more than 8 h a day. Due to strict protection requirements, medical staff can barely drink water when sampling, and it is inconvenient to go to the toilet. All these factors may cause high work pressure on both physical and mental aspects among nucleic acid collectors.

Previous studies have found that frontline workers are prone to a range of psychological problems, including fear, depression, anxiety, post-traumatic stress symptoms and insomnia during high-risk and stressful situations during the pandemic (11–13). For example, a large proportion of healthcare workers battling SARS suffer from depression, anxiety and sleep problems (14, 15). Recent studies have shown that health workers have higher psychological problems during COVID-19 than in past epidemics (16). Several studies have shown that physical, emotional, and mental health can all be impaired by overwork (17–20). The potential negative psychological impact is not only detrimental to the growth of medical staff, but also may reduce effective response to emergencies (11, 21).

At present, there have been many investigations on the anxiety and depression of medical staff in the fight against the epidemic. But during the strict closed-loop management, nucleic acid collectors face great physical and mental challenges, and there are few studies on the impact of such management methods on psychological state. The purpose of this paper was to conduct a preliminary psychological evaluation of nucleic acid collectors who participated in closed-loop management during the Omicron epidemic in Xi'an, and analyze the influencing factors to provide a scientific basis for later psychological recovery.

This study analyzed the psychological status of 1,014 nucleic acid collection staff in Shaanxi Province under closed-loop management through monofactor and binary logistic regression models. And the research found a high proportion of nucleic acid collectors with depression, anxiety and sleep disorders during closed-loop management. Age, technical title, education level, collection time, collection frequency, collection location, fear for infection and external environment also affected the psychological state. The PHQ-9, GAD-7 and PSQI used in this study are mainly used for clinical screening for depression, generalized anxiety disorders and sleep disorders. When PHQ-9 and GAD-7 scores ≥ 10 points, PSQI ≥ 7 points, usually considered that the patients may have depressed mood, anxiety or sleep disorder problems and need further diagnosis (25, 26).

First, the incidence of depression, anxiety and sleep disorders among nucleic acid collection personnel throughout the closed-loop management period were 33.5, 27.2, and 50.1%, respectively. Previous research showed that during the epidemic, 14.3% of clinical doctors and nurses suffered from depression, 11.2% from anxiety (33), and 61.67% (34) from sleep disorders. During the non-epidemic period, the incidence of depression, anxiety and sleep disorders of medical staff were 1.98%, 6.52% (35), and 39.2% (36), respectively. Moreover, compared with more research data from other countries on the incidence of depression, anxiety and sleep disorders among medical personnel during the COVID-19 pandemic. The incidence of depression, anxiety and sleep disorders were 36, 34, and 52%, respectively in Spanish medical personnel (37); 37, 23, and 34% in Latin America (38); 55, 51, and 28% in Africa (39); 34%, 46% (40), and 40% (41) in Eastern Europe. And the prevalence of depression, anxiety and sleep disorders among health-care workers in south-east Asia were generally lower than other regions during the pandemic, which were 14, 23, and 18% (42), respectively. Therefore, the prevalence of mental health symptoms during the COVID-19 pandemic is not homogeneous across different regions. Compared with the results in this study, the incidence of depression and anxiety in above countries are much higher. On the one hand, different research tools may lead to differences results. On the other hand, since the COVID-19 outbreak, the world has experienced many waves of the epidemic, medical staff's mental state is also different from the beginning. Moreover, the different incidence of depression, anxiety and sleep disorders between different countries are more likely related to region, cultural and political factors. For instance, African health-care workers have the highest rates of depression and anxiety in these countries, and it may be that in economically underdeveloped areas, the incidence of infectious diseases is high, health facilities are poor and mental health receives less attention (39). These are likely to lead to an increase in the incidence of depression and anxiety in health-care workers. On the contrary, the incidence of sleep disorders among nucleic acid collection personnel in this study is higher than in other countries. It was hypothesized that researchers and nucleic acid collectors were engaged in long-term epidemic prevention, which leading to high mental stress and heavy workload. In addition, frequent shifts, lack of sleep also increased the risk of infection during closed-loop management. The sudden outburst of this highly infectious disease and the containment measures such as quarantine and social distancing have posed immense pressure on the work and life of the health-care workers (43). This could lead to an increased incidence of sleep disorders among the nucleic acid collection staff.

Second, this study examined the correlation between the research variables among the nucleic acid collection staff. The higher the score on the depression and anxiety scale, the higher the total score of sleep disorder, indicating that medical staff sleep quality is poor. At the same time, when the sleep disorder score increased, the occurrence of depression and anxiety increased. The age of the nucleic acid collection staff was positively related to depression and anxiety, indicating that the older the patient, the more likely he or she was to suffer from depression and anxiety, the present study findings are in line with other reports (35, 44). Younger adults, however, appear to be more susceptible to sleeplessness and anxiety, according to Wang et al. (45). The discrepancy may be caused by older medical staff members' worse health state in terms of nucleic acid collection and their decreased tolerance and capacity to adjust to cold and demanding work situations compared to those under the age of 40. Depression, anxiety and sleep disorders were negatively correlated with education level, that is, the higher the education level, the lower the incidence of depression, anxiety and sleep disorders. Among people suffering from serious physical health problems, those with higher education were less likely to experience symptoms of depression and anxiety than those with lower education. Higher levels of education help to regulate the relationship between psychological and stress responses, thus reducing the occurrence of depression and anxiety (46, 47). The findings showed that fear for infection was positively associated with depression, anxiety and sleep disorders, which was because the outbreak of COVID-19 is the largest public health emergency in China in the past decade (48). At the same time, the developing Omicron variant has a high incidence and expands quickly (49). In the short term, there were many more confirmed cases in Xi'an, which can add to their psychological strain.

By analyzing data from a binary logistic regression model, we discovered greater positive rates of depression and anxiety among the mobile cabin hospital collecting staff than at other collection locations in the current research. The results of the analysis revealed that the collection personnel had extended direct contact with the sampled subjects (positive patients) and that this increased both parties' risks of infection or cross-infection compared to those in the community or schools. According to other research, medical professionals working in high-risk situations are more likely to experience depression, anxiety, and sleep difficulties as well as higher levels of “fear about infection” than those working in low-risk conditions (50). Similar to door-to-door nucleic acid collection, floor-by-floor sampling by medical professionals raises the risk of aberrant psychological situations under heavy load and external environmental effects. As evidenced by the frequency and duration of nucleic acid collection, the intensity of nucleic acid collection is relatively high and overload is more common. Among them, 79.1% were overloaded. Previous research has shown that prolonged and intensive work tends to worsen medical personnel's mental health (51). In addition, the heavy workload may make medical staff more susceptible to illness and the shifts in the outside environment will have an impact on collectors' attitudes. Previous studies have shown that the weather to some extent affects the psychological two important factors are the season and outdoor time (52). In January, the temperature outdoor Xi'an was relatively low, and the collecting staff worked longer in the low-temperature environment, which was more likely to lead to negative emotions than the more comfortable indoor environment.

The public was poorly informed about the mental health implications of the SARS pandemic when it first appeared in China, and those who need it did not receive any specific psychological support. In public health emergencies, the intensity and duration of medical staff increases, the risk of infection increases, and they face greater physical strength and mental stress, which leads to the occurrence of depression and anxiety, which is seriously affected sleep quality (53, 54). Staff members who performing nucleic acid collection always get physically and mentally exhausted during a protracted period of epidemic preparation, particularly during line-points closed-loop management. The suggestions are as follows. First, the staff can engage in appropriate physical exercise during closed-loop management to reduce psychological stress and relieve psychological tension. Second, relevant management departments should strengthen human resources to improve detection efficiency, optimize nucleic acid collection process, reduce the workload of nucleic acid collection staff, and improve the working environment for nucleic acid collection. Finally, the mental health status of nucleic acid collection medical staff should be investigated regularly and corresponding psychological assistance measures should be taken to alleviate depression, anxiety and sleep disorders of nucleic acid collection personnel under closed-loop management.

There are some limitations in this study. First, we used a practical sample strategy based on an online questionnaire survey, which made our sampling dependent on the online network environment and potentially prone to selection bias. Second, it has a cross-sectional design which limits the ability to interpret the causal relationships between the different variables in this study. The association and causality can be more accurately determined in randomized prospective research. Finally, since the scope of our study was restricted to Shaanxi Province and the sample size was modest, a bigger sample size is required for the validation of our findings.

The original contributions presented in the study are included in the article/supplementary material, further inquiries can be directed to the corresponding author.

The Ethics Committee of the Affiliated Hospital of Shaanxi University of Traditional Chinese Medicine, Shaanxi Province, China approved this study (Ethical number: 2022-0516). The patients/participants provided their written informed consent to participate in this study.

MS implemented this study and was responsible for data collection and analysis and writing. XL, JY, and YK took part in the process of data collection. XH and ZL provided assistance in reviewing the manuscript. All authors contributed to the article and approved the submitted version.