Human coronaviruses (HCoVs) are highly pathogenic viruses that infect the human respiratory tract. They were first isolated from the nasal secretions of patients with cold symptoms in 1965 and named B814. Due to the crown-like spikes on their surface under electron microscopy, they were also named HCoVs. This type of virus generally has a consistent gene structure and protein expression. In mild cases, HCoVs infect the human upper respiratory tract and the gastrointestinal tract and cause colds and diarrhea, i.e., a self-limited disease. In severe cases, HCoVs can cause bronchitis and pneumonia and even affect multiple organs, leading to death. According to phylogeny, HCoVs are divided into 4 subgroups, i.e., ɑ-CoV, β-CoV, γ-CoV and δ-CoV . Thus far, there are 6 HCoVs that can infect people, and 2 have high infection rates and mortality rates. One such HCoV is SARS-CoV, which causes severe acute respiratory syndrome (SARS); an outbreak in 2002-03 spread to 29 countries and regions around the world, resulting in 8546 infections and 809 deaths, with a mortality rate of 9.6%; however, the mortality rate in older populations is estimated to be over 50%. Another HCoV is MERS-CoV, which causes middle east respiratory syndrome (MERS), first discovered in Saudi Arabia in 2012. At the end of 2015, it caused at least 1621 infections in 26 countries and regions around the world, resulting in 584 deaths and a mortality rate of more than 36% . After infection, the early symptoms of MERS-CoV are atypical, with subsequent severe respiratory distress and pneumonia. About one-third of patients develop gastrointestinal symptoms including vomiting and diarrhea, showing a high mortality.
2019-nCoV is an enveloped plus single-stranded RNA virus with a diameter of 60-140nm. The spikes of barrel-shaped glycoproteins in the envelope give the virus a crown-like appearance. The whole-genome sequencing of 2019-nCoV showed an 86.9% nucleotide sequence identity with the previously identified bat SARS-like coronavirus genome (bat-SL-CoVZC45, MG772933.1) . Its infection characteristics are also similar to those of SARS-CoV; that is, the respiratory symptoms are severe, the gastrointestinal symptoms are mild, and the disease progresses rapidly. However, according to the public information currently obtained, it is highly contagious and can spread between people. Individuals with latent infection and no symptoms are also contagious. Person-to-person spread is thought to occur mainly via respiratory droplets and close contact. 2019-nCoV has also been found in the stool samples of patients [4,6]; however, whether 2019-nCoV can spread in this way is still unclear. The Chinese population is generally susceptible to 2019-nCoV. The latent period generally ranges from 3-7 days; the longest latency period has not exceeded 14 days. Nonspecific symptoms at the early stage of infection include fever, fatigue, dry cough, sore throat, myalgia, etc. Early routine blood results indicate normal or decreased white blood cell count, reduced lymphocyte count, and, in some patients, elevated liver enzyme, muscle enzyme, and lactate dehydrogenase levels. Severe cases involve elevated serum D-dimer levels and progressively reduced peripheral blood lymphocyte counts. Nucleic acid of 2019-nCoV can be detected in throat swabs, sputum specimens, lower respiratory tract secretions, blood and fecal specimens. In the early stage, chest imaging results show multiple small plaque shadows in the peripheral lung, developing into multiple ground glass opacities and infiltration shadows in both lungs. In severe cases, lung consolidation may occur, but pleural effusion is rare. Approximately 50% of patients develop dyspnea after 1 week, and in severe cases, the disease progresses to acute respiratory distress syndrome (ARDS) . For male patients, senior patients, patients with multisystem diseases and patients with underlying pulmonary diseases, critical conditions are more prone to occur, and non-improved respiratory failure and persistent hypoxemia after treatment are associated with a high risk of death. ECMO treatment is an effective method to help critically ill patients . Although the first patient in the United States achieved good results using remdesivir , its efficacy and safety still need to be verified by large-scale clinical trials. Remdesivir is currently undergoing clinical trials in a 2:1 ratio between the treatment group and the control group.
The current data show that 31774 cases have been diagnosed nationwide; 6101 were severe cases, and 27657 were suspected cases, with 722 deaths (data up to 23:59 on February 7, 2020). The mortality rate is 23.3% in China, and severe cases account for 19.2%. Currently, the observed mortality for 2019-nCoV is lower than that for SARS-CoV and MERS-CoV, but the ability to spread is stronger, with a large number of infections. The development of the outbreak cannot be underestimated, and effective isolation is still the best method to control the spread. The 17 deaths in this study indicate that the risk of death is higher in elderly patients with underlying diseases. At present, hypertension accounts for a relatively high proportion of observed underlying diseases. Studies have shown that there are 6 predictive factors for the risk of death from pneumonia: multiple lobar infiltrates, lymphocyte reduction, mixed bacterial infection, smoking history, hypertension, and age. The majority of the 17 patients were elderly and had hypertension. Hypertension is also a common underlying disease in elderly patients. Whether hypertension increases the affinity of patients to the virus and contributes to the spread of the virus remains to be revealed by further research.
In this study, only 2 of the 17 patients were tested for the 2019-nCoV pathogen, and the results were positive. However, due to the time required for virus isolation and nucleic acid sequencing and the shortage of clinical nucleic acid detection reagents, the remaining 15 patients did not undergo etiological examinations. However, in the early stage of an outbreak with limited resources, chest imaging (chest CT) can more directly aid clinical diagnosis. In this study, all the imaging results pointed to viral pneumonia, indicating that death was caused by NCIP. Additionally, due to the different development stages of disease and the varying quality of respiratory tract samples, not all patients whose etiological examination was negative can be excluded. Clinical diagnosis based on early clinical symptoms of disease combined with changes in chest imaging should implemented when resources are insufficient. Isolating older people is an effective way to reduce mortality.