In this study, the epidemiology, early clinical features, serological and radiologic changes of 7 confirmed patients were summarized, and the clinical evolution of the disease was obtained by analyzing the dynamic changes of laboratory and imaging. Our 7 patients were composed of common and severe type. During the treatment of common type patients, we observed the process of transformation to severe type accompanying serological and imaging changes. Through timely treatment, 3 severe patients were successfully treated. We had observed the complete progress from the normal type to the severe type, and the recovery process of severe type.
All seven patients had a clear history of epidemiology, either from or in contact with people from epidemic areas including 2 family cluster cases. The outbreak was approaching the Spring Festival, the movement of people accelerated the spread of the epidemic. Timely measures such as "close-off cities" in time, isolating people came back from epidemic areas and reducing the number of residents going out for parties had played an important role in preventing the spread of the epidemic during the Spring Festival.
In terms of clinical features, the main clinical manifestations of 6 patients were respiratory symptoms, most of which were mild. Only 2 cases came to see a doctor because of fever, and monitoring body temperature alone may not be able to discover potential infected patients. Notably, in one case the first nucleic acid test was negative, but positive for the second time. For high-risk groups, re-examination of throat swabs is necessary. The symptoms of two patients were mild and the progression of pulmonary imaging in a short time was obviously, who classified as severe type later. It is necessary to closely observe the common type patients whose clinical symptoms and pulmonary imaging changes are not serious, especially those age older than 50 years with underlying diseases.
Serologically, 7 patients showed no elevation of PCT, whether normal or severe type, mild or severe pulmonary lesions.This finding might be due to COVID-19 as viral infections and the use of antibiotics during treatment to prevent secondary infections
There was no significant change in the absolute count of blood lymphocytes in the common type patients, but the absolute count of lymphocytes in the severe type patients decreased suddenly during the course of the disease, and gradually increased after the improvement of the disease, which was consistent with the report of Liu et al.[12]. Bilirubin or aminotransferase abnormalities were observed in all patients during the course of the disease, which may be caused by drugs or associated with systemic inflammatory responses[13]. The renal function tests of all patients were normal, which was consistent with the report of Wang et al.[14]. In common type and severe type patients, abnormal liver function was common, renal function abnormality was rare, and PCT was normal when without secondary infection. There were individual differences in the absolute count of blood lymphocytes and the changes of serum albumin and globulin. The changes in patients with severe pulmonary lesions (Fig. 1b, 1d, 1e, 1f) were more obvious than those in common type patients (Fig. 1a, Fig. 1c, Fig. 1g). In severe type patients, the absolute count of lymphocytes decreased in the course of treatment, accompanied by the increase of serum globulin and the decrease of serum albumin, and finally serum globulin level exceeded serum albumin, resulting in the phenomenon of A/G inversion. After the serum globulin level reached its peak, serum albumin began to rise and the absolute count of lymphocytes began to rise too. The change of serum albumin and globulin was less likely to be caused by exogenous transfusion of blood products, and this phenomenon was not observed in the treatment of other diseases with high-dose immune globulin[15, 16]. The decrease of serum albumin and the increase of serum globulin were found in 6 cases before the specific antibody could be detected, which may be related to the activated host immune system, resulting in an increased antibody production by B cell and above changes in serology. According to the exclusion criteria of suspected cases in the seventh edition of the national diagnosis and treatment plan, the diagnosis of suspected cases can be excluded if SARS-CoV-2 specific antibodies IgM and IgG are still negative 7 days after onset[10]. In data of our confirmed patients, the time period of the specific antibody could be detected was 5–13 days after the onset of symptoms, which suggested that the time setting for excluding suspected cases should be different when using different detection kits.
The imaging changes of the lungs in severe patients were dynamic process. The acute exudation of the lungs were associated with the decrease of the absolute count of blood lymphocytes, and the lesions were gradually absorbed and striped after effective treatment. Significantly, acute exudative changes in lung lesions in common type patients developing to severe type were accompanied by a decrease in the absolute count of lymphocytes, which occurs before specific antibodies could be detected. The appearance of specific antibodies may be related to the decrease of the absolute count of peripheral blood lymphocytes and the progress of pulmonary imaging in severe patients. It is necessary to pay attention to whether the antibody dependence enhancement (ADE) effect was exist just as SARS virus. The study of SARS virus found that it could not directly infect lymphocytes which lacking ACE2 receptors, and lymphopenia during the disease process was likely caused by lymphocytes apoptosis or necrosis through indirect mechanisms[17]. In vitro experiments showed that SARS virus could infect lymphocytes by ADE effect through FcγRII[18, 19]. Excessive activation of T lymphocyte function due to pulmonary immune response may be responsible for the decrease in absolute lymphocyte values in severe and critical patients. Previous studies have shown that SARS specific antibodies were associated with lung immune damage. Acute lung injury occurred in Chinese rhesus macaques vaccinated with the SARS-CoV two days after intravenous injection of anti-spike IgG (S-IgG), which was similar to that of SARS-CoV infection of human[20]. This effect is related to viral load, antibody level and FcγRII polymorphism[21]. Autopsy of the patients with COVID-19 showed that the changes of lungs were similar to those of SARS and middle east respiratory syndrome (MERS), which mainly showed severe immune injury. At the same time, it was accompanied by excessive activation of T lymphocytes and decrease of peripheral blood lymphocytes[22]. The pulmonary imaging changes CT shown were associated with inflammation caused by immune response. In our patients, 2 cases of common type converted to severe type were accompanied with lymphocytopenia and obviously pulmonary imaging progressed, acute pulmonary exudation was absorbed and the absolute count of lymphocytes increased after treatment with glucocorticoid and high-dose human immune globulin in time. The effectiveness of the treatment also suggested that the changes of serology and imaging were related to immune factors.
Combined with the above clinical data and literature, we speculated that in the process of immunological clearance of SARS-CoV-2 virus, the virus proliferating in the incubation period and the specific antibodies secreted by host immune cells produce antigen-antibody immune reaction in the lungs. There are individual differences in this response, and patients with high viral load and severe immune response have decreased absolute count of lymphocytes and obvious progress of pulmonary imaging, which are severe type and critical type patients. In the treatment of COVID-19, antiviral therapy to inhibit viral replication is the basis. Close observation of the changes of the patient's condition and timely use of appropriate amount of glucocorticoid and human immune hemoglobin or other drugs regulating immune response at the stage of severe development of the disease would help to control the disease. During the treatment, the dynamic changes of absolute count of blood lymphocytes, serum albumin and serum globulin can be used as a reference for judging the disease progress. The decrease of absolute count of lymphocytes, the decrease of serum albumin and the rise of serum globulin form the first cross to indicate the progress of the disease, suggesting that it is possible to be severe type. We have observed that the appearance of SARS-CoV-2 specific antibodies may be related to the progression of lung disease, and whether SARS-CoV-2 virus has the ADE effect similar to SARS virus remains to be studied in the future.
COVID-19 patients with individual differences in the development of the disease are often at different stages of the disease on admission. At the same time, some clinical indicators of the patients change significantly. The present research about the evolution of the disease through cross-sectional analysis were not accurate enough, and there is no dynamic analysis of serological and imaging changes. In clinical work, the clinical, serological and imaging changes of patients are not isolated, but synchronously developed and related to each other. Understanding the rules is helpful to the clinical treatment and the study of the pathophysiology of the disease. Through the analysis of the progression from common type, common type to severe type and severe type patients, we spliced out the dynamic evolution of COVID-19 and described the disease development more accurately. This will help us to understand the nature of the disease and guide clinical treatment.