The first confirmed patient with COVID-19 in Shandong Province was a 37-year-old male from Wuhan who worked in Rizhao City. He was treated in Rizhao and Qingdao due to fever and other symptoms. He had lived in Wuhan within two weeks before and he was admitted to the hospital for isolation and treatments. On January 21,the expert group evaluated and confirmed that he had infected COVID-19. At the same time, the Shandong Novel Coronavirus Leading Group immediately arranged epidemic prevention and control works and emphasized the on-duty requirements of key positions, and strictly implemented the "daily report, zero reports" rules. Since then, in the face of the gradual increase in the number of confirmed cases per day, Shandong Province launched a Level I response to major public health emergencies on January 24 to mobilize the entire province to curb the spread of the virus. Over time, the number of daily confirmed cases in Shandong Province increased to the highest on February 5 and then showed a downward trend. The growth rate of the cumulative confirmed cases fluctuated before January 27, but gradually declined from January 28. The stabilization indicates that the incidence of pneumonia caused by the COVID-19 in Shandong Province had slowed down and that the series of prevention and control measures implemented in Shandong Province were effective.
From the above studies, as of February 15th, most of the patients diagnosed with COVID-19 in Shandong Province were mild or moderate. Severe rate is 2.98%, and the fatality rate was 0.37%, which was lower than the number of confirmed cases in Chongqing Province which was 537 Cases in that time; the critical rate was 2.23%, which was lower than that of Shanxi Province; the cured rate was 30.54%, which was higher than the cured rate in Chongqing and Shanxi Province. This might be related to the actual conditions faced by different provinces and cities, and to a certain extent indicated that the diagnosis and treatment measures in Shandong Province were effective.
The results of this study show that there were more males than females in the confirmed cases, and the male-to-female ratio was 1.26:1, which similar to the findings of Ou Jianming et al. and slightly higher than the research results of COVID-19 Emergency of the Chinese Center for Disease Control and Prevention and Response Mechanism Epidemiology Group. Compared with women, men are more mobile and have a wider social network and groups. In the passenger and cargo transportation, logistics, express delivery, and other industries, the number of men employed is significantly higher than that of women, so men are more susceptible to infection. In the age distribution, the oldest confirmed case was 91 years old and the youngest was only 9 months. There were infected persons in all age groups, indicating that the virus was generally susceptible to infect all age groups. The age of the patients was concentrated in the range of 30–59 years old; most were middle-aged and young people. It may be that this age group is active, socially extensive, and contacts with many people, which may increase the risk of infection. This study also finds that there were more female patients whom more than 60 years of age, and more male patients under 60 years old than female patients, which may be related to differences in male and female physiological characteristics.
Judging from the travel, residence and contact history of confirmed cases, the cumulative number of confirmed cases with a history of travel,residence in other places rather than Shandong and Hubei before February 6 was higher than the cumulative number of confirmed cases with a history of contact in Hubei and a history of close contact with confirmed cases. This was mainly because of the initial outbreak of the epidemic coincided with the Spring Festival. Factors such as the flow of people, vacations, and the increase of the migrant population in a short period provided favorable conditions for the further spread of the epidemic. Studies show that the development of the COVID-19 epidemic or pandemic was related to the level of population mobility. Frequent population mobility was extremely conducive to the spread of infectious diseases. After that, the number of patients with a history of close contact with the confirmed case increased rapidly and quickly exceeded the number of cases with a history of living or travel in other places rather than Shandong and Hubei, and a history of contact in Hubei in a short time, indicating that the local epidemic spread rapidly through contact, which gave rise to what Academician Zhong Nanshan said "super spreaders" and second-generation cases. By reviewing the case data, it is known that Zhang XX from Weifang, Shandong and Tian XX from Heze, Shandong deliberately concealed their travel, illness, and close contact history, resulting in a total of more than 100 people being isolated and causing a local epidemic and the disease spread rapidly and multiple infections. After February 10, the cumulative number of confirmed cases with a history of travel or residence in other places rather than Shandong and Hubei, a history of contact in Hubei, and a history of close contact with confirmed cases had slowed down, which further illustrated that Shandong Province initiating the highest-level response to detect and control the infection in the first time was effective. Measures such as blocking possible transmission channels and protecting susceptible populations had effectively curbed the spread of the epidemic.
The Temporal and spatial distribution map of confirmed cases of COVID-19 in Shandong Province shows that during the epidemic, the first confirmed patient was confirmed in Qingdao, and as of February 15, the city had the highest number of cases in Shandong. As an open coastal city and an economically developed city in northern China, Qingdao was affected by factors such as climate, geography, economy and social culture and dense population and developed transportation, coupled with a large flow of population, were extremely conducive to the spread of the virus.
There were no confirmed patients in Dongying City. The reason was not only that the government and relevant departments took timely and early measures to curb the spread of the epidemic in Dongying, but it might also be due to other factors of Dongying City. For example, comparing with densely populated areas with convenient transportation, Dongying City had a low population density, underdeveloped railway and air transportation, and high per capita GDP and fewer migrant workers, making it less likely to have close contact with people from Hubei. From the perspective of the national epidemic situation, Tibet, Qinghai, and other western regions in China; there were sparsely populated areas and relatively underdeveloped transportation had fewer confirmed cases. The characteristics of the epidemic in Dongying were also consistent with some of the characteristics of the national epidemic distribution. Therefore, taking targeted joint prevention and control measures according to the characteristics of the area is an effective means to reduce the incidence the outbreak.
Although the research results show that the incidence of COVID-19 in Shandong Province has slowed down, it is also facing pressure from resuming work, resuming production, and returning to school. Besides, the global pandemic situation is severe and the vaccine is still in the experimental stage, COVID-19 prevention and control still cannot be relaxed. Therefore, based on the epidemiological characteristics of the COVID-19 and the latest developments and changes of the epidemic or pandemic, the future response strategies for prevention and control are given as follow:
First and foremost, construct a multi-level public security intelligent monitoring, early warning, and control system. Further expand the monitoring network, improve big data analysis technology, enhance early monitoring and early warning capabilities, and realize real-time intelligent epidemic warning[21–23]. Improve the real-time query system for epidemic risk levels and comprehensively promote the use of health passcodes (or health virtual pass cards) across the country to further accurately identify people form high, medium, and low-risk areas. The construction of monitoring, early warning, and control system for diseases of unknown origin and emerging infectious diseases should be established.
Moreover, scientifically and rationally allocate and utilize existing medical and health resources, and improve the joint prevention and control work mechanism. For large general hospitals and infectious disease hospitals, training bases for epidemic prevention and control should be established; emergency management departments, disease control departments, lower-level hospitals, and primary health institutions need work together to conduct regular epidemic prevention and control-related training and drills to strengthen and improve multi-departmental collaboration and upper-lower level linkage mechanisms. For county-level general hospitals, independent infectious disease departments should be set up, and existing outpatient clinics and wards should have the ability to be transformed base on the combining peace and war principles, and should equip with negative pressure wards, and negative pressure ambulances to ensure that if an outbreak occurs, it can be reached quickly for emergency treatment of critically ill patients. For primary health institutions such as village clinics and community health service centers (stations), efforts should be made to build fever screening sentinels to enable them to have early screening capabilities, give full play to the role of sentinel surveillance against the epidemic or pandemic, and preliminary screening, identification, treatments, and referral of fever patients are effectively carried out to effectively "early detect and report" the outbreak, which is more conducive to the epidemic prevention and control. For centers for disease control (CDC), it is necessary to establish a certain scale of epidemiological investigation teams in each county and district, and increase investment in efforts to laboratory construction, and support to do more scientific researches to accelerate vaccine research and development.
Besides, effectively carry out the epidemic investigation, prevention and control of the flow of population, implement strict entry-exit inspection and quarantine measures, continue to implement travel registration and body temperature testing systems. It is necessary to continue to strengthen the disinfection and ventilation of public places, adopt flexible working hours to reduce the number of people gathering. .
Last but not the least, attach importance to social mobilization, strengthen health education, communication, increase the public's initiative and motivation for epidemic prevention and anti-epidemic, and encourage the public to take the initiative to pay attention to infectious diseases and epidemic-related information and report the epidemic to relevant professional agencies in time. Governments and relevant professional institutions should incorporate the social risk early warning force of major epidemics into the formal public opinion monitoring and release system so as to timely verify and scientifically screen the information. It is necessary for us to continue to strengthen the breadth and depth of health education, increase public awareness of the COVID-19. Carry out online health education and consulting services to enhance the public’s protection awareness.