consolidation; common laboratory findings are lymphopenia and/or leukopenia. [5] [6] [7] [8] [9] According to the practice guidance for diagnosis and treatment of novel coronavirus pneumonia in China (7th trial version) issued by the China National Health Commission, COVID-19 is diagnosed on the basis of epidemiological history and clinical symptoms as described above, combined with confirmed infection of SARS-Cov-2 through one of the following methods: real-time reverse transcription-polymerase chain reaction (RT-PCR) assay, high-throughput genome sequencing, and serological measurements of antiviral immunoglobulin M (IgM) and G (IgG) antibodies. It is worth noting that it has been previously reported that some individuals infected with SARS-CoV-2 are asymptomatic when RT-PCR tests are confirmed positive, [10] [11] [12] [13] and some patients that recovered from COVID-19 have positive RT-PCR results again at follow-up. 14 Previous reports indicate that most COVID-19 patients are middle-and old-aged, often with underlying conditions such as hypertension, diabetes mellitus, and coronary heart diseases (CHD), especially in severe cases. 9, 13 However, chronic obstructive pulmonary diseases (COPD) are relatively less common in COVID-19 patients, with a prevalence of 1.1%-2.9%. [7] [8] [9] In a study involving 140 cases with COVID-19 on the association between allergies and infection, no patients were found to have asthma or allergic rhinitis. 8 As for SARS-CoV-2, a novel virus, there are still unmet research needs to further characterize its clinical profile. 15 The more we investigate the clinical situations and characteristics of COVID-19, the more lessons and knowledge we obtain. In this article, eleven con- Main clinical data and laboratory results are tabulated in Tables 1 and 2, respectively.
A 26-year-old male nurse was screened for COVID-19 on February 14, 2020, after contact with an infected person. RT-PCR assay with an oropharyngeal swab sample tested positive for SARS-CoV-2.
Chest CT images showed no signs of pneumonia. The patient was admitted to the isolated ward and treated with antiviral drugs including Arbidol and Prezcobix (darunavir and cobicistat tablets). All laboratory results were within normal ranges. The patient was discharged 4 days later after testing negative in two consecutive RT-PCR assays. The patient did not experience any symptoms before and during hospitalization.
On January 19, a 22-year-old female medical staff began to have a sore throat with dry cough after a night shift, without developing rhinitis. Symptoms were relieved by oral common cold medications including Chinese traditional medicine (CTM). She felt discomfort with myalgia on January 25 and tested positive for SARS-CoV-2,
Clinical manifestations of COVID-19 range from asymptomatic cases to patients with mild and severe symptoms, with or without pneumonia. Laboratory detection of the viral nucleic acid can yield false-negative results, and serological testing of virus-specific IgG and IgM antibodies should be used as an alternative for diagnosis. Patients with common allergic diseases did not develop distinct symptoms and severe courses. Cases with a pre-existing condition of chronic obstructive pulmonary disease or complicated with a secondary bacterial pneumonia were more severe.
as detected in a RT-PCR assay with an oropharyngeal swab specimen. The complete blood count (CBC) was within normal ranges, and chest CT scan was negative for any signs of pneumonia. Two additional RT-PCR results (January 31 and February 7) were positive for novel coronavirus nuclear acid and with normal chest CT images on both days. She was admitted to the designated hospital on February 9. During hospitalization, all the CBC and biochemical measurements were in normal ranges, and the chest CT scan on February 15 remained normal. She experienced only mild symptoms such as a sore throat and fatigue, without any signs of pneumonia such as cough and chest tightness. The patient recovered after treatment with antiviral therapy (Arbidol) and supportive care. She was discharged on February 22 after three consecutive negative RT-PCR results. We suggest that this case represents a mild COVID-19 without pneumonia.
After contacting with feverish patients, a 42-year-old woman developed fever, with a maximum temperature of 38.7°C, accompanied by a dry cough and sore throat on January 23. An immediate chest CT scan at the designated clinic showed normal images. She was selfisolated at home and took some common cold medications, CTM and antipyretics to relieve symptoms. The fever ameliorated but the cough persisted. A week later, a second chest CT scan revealed pneumonia in the left lung ( Figure 1A ). An oropharyngeal swab specimen was collected and tested negative RT-PCR for the novel coronavirus nucleic acid. Despite treatment with antipyretics, her fever reap- With significant reduction in clinical symptoms and CT manifestations, the patient was discharged on March 1. We suggest that this case represents a COVID-19 pneumonia without detectable virus in oropharyngeal specimens.
A 44-year-old man was admitted to the designated hospital as COVID-19 infection was confirmed on February 2. Symptoms included cough, dizziness, and fatigue for one week, with bilateral ground-glass opacities on chest CT images. RT-PCR on the throat swab sample was positive for SARS-CoV-2. Most laboratory tests were within normal ranges, except for mild leukopenia Even though he was asymptomatic, he was readmitted to the hospital two weeks later as he tested positive in a RT-PCR assay for SARS-CoV-2 using a sample collected from an oropharyngeal swab. During the second hospitalization, the CBC and all biochemical tests were within normal ranges. He remained in the hospital as SARS-CoV-2 detection by a RT-PCR assay was positive on March 3 and 7. We suggest that this case is representative of a long-term virus carrier. Abbreviations: Abs, antibodies (against the virus); CAP, community-acquired pneumonia; COPD, chronic obstructive pulmonary disease; ECMO, extracorporeal membrane oxygenation; NA, not available; RT-PCR, real-time reverse transcriptase-polymerase chain reaction (for detection of viral nucleic acid). a Supportive therapies were included in the treatments for all the cases. Antibiotics were ceftriaxone and moxifloxacin initially and changed to cefoperazone sulbactam, linezolid, and polymyxin later. 
After contact with children with a cough, a 28-month-old boy began to cough and developed a strong fever (39.2°C) two days later. He was admitted to the hospital a week later on January 28. According With the relief of symptoms and two consecutive negative RT-PCR results, he was discharged on February 6. This patient was a pediatric case with COVID-19 pneumonia with a background of atopic dermatitis. week showed partial absorption of lesions ( Figure 6B ). The patient's symptoms, including diarrhea, disappeared a few days after treatment. After two consecutive negative results of viral nucleic acid tests, she was discharged on February 20. This case is of high interest as the patient experienced diarrhea in the initial symptoms.
Herein, we present eleven different clinical manifestations of COVID-19. Apart from the asymptomatic case in our report, several previous case reports have also described the absence of any symptoms in patients with laboratory-confirmed COVID-19, and they even retain the ability of disease transmission. 10, 16 It is of particular interest to investigate if the asymptomatic cases are caused by the immune system, viral load, or a different attenuated viral strain. 17 In these cases, the virus has been detected in the pharyngeal specimens, and it is very unlikely to have a different strain in this epidemic condition.
It is possible that the virus did not sufficiently stimulate the innate immune response to develop symptoms of fever and fatigue. In addition, there were no respiratory symptoms, such as cough, suggesting a low-level mucosal irritation. Asymptomatic but infective status has been reported in many viruses, such as respiratory, hepatitis, and diarrhea viruses, as well as in other major human viruses, such as cytomegalovirus or herpes viruses. [18] [19] [20] In a recent COVID-19 study, the viral load in upper respiratory specimens of asymptomatic patients was found in similar levels to that of symptomatic patients, suggesting a similar transmission potential of asymptomatic or minimally symptomatic patients. 21 Not only can the virus be detected in fecal specimens, 22 but also the viral nucleic acid testing on rectal swabs remained positive even after nasopharyngeal testing had become negative. 23 The RT-PCR assay for viral nucleic acid is the current "gold standard" method to detect SARS-CoV-2 and diagnose confirmed cases. We presented two pediatric COVID-19 patients, with either a history of allergic rhinitis or atopic dermatitis, which are common allergic diseases in children. As we reported in a recent study, allergy does not appear to be a predisposing factor for COVID-19. 8
The two children presented as ordinary types of COVID-19 and were both treated with interferon-α inhalation as a nonspecific antiviral therapy, which was one of the trial methods recommended in the practice guidance of novel coronavirus pneumonia in China.
The adult patient with chronic urticaria in case 9 was also classified as an ordinary type as well. These and previous results indicate that allergic diseases may not be an aggravating factor of the disease. Previous studies have demonstrated that respiratory virus infections represent risk factors for asthma exacerbation and even have prolonged impact on the development of asthma. 28, 29 Given the association between virus infection and asthma, 30 