Beginning in December 2019, 41 cases of unexplained pneumonia occurred in Wuhan, Hubei Province, China. As a major transportation hub, Wuhan is about 300 kilometers away from Jiangxi.
Respiratory viruses can cause symptomatic infection at any age and at any location in the world. However, respiratory viruses are prone to antigen drift due to point mutations in the virus genome, resulting in the formation of new strains with pandemic potential. All these factors can increase the difficulty of rapid and accurate diagnosis of respiratory diseases. Therefore, it is necessary to identify mutations in the virus genome and understand the gene sequence of the new virus.
SARS is a zoonotic disease caused by SARS-CoV. Hospital transmission of SARS-CoV is very common. The main host is bats, and the intermediary is mosquitoes from the Guangdong wet goods market (Azhar et al., 2019). Middle East Respiratory Syndrome (MERS) is a new zoonotic deadly disease caused by the Middle East MERS Coronavirus (MERS-CoV), which appeared in 2012. It is believed that humans became infected with MERS-CoV through exposure to camels or camel products, and a lethal rate of approximately 35% was observed.
After detecting this new coronavirus, a Chinese science team announced at a national press conference that this was the pathogen that caused the epidemic, and the WHO designated the virus as the new coronavirus in 2019 (2019-nCoV) (Xinhuanet News Report, 2020). On February 12, pneumonia infection with the new coronavirus was collectively referred to as severe acute respiratory syndrome coronavirus 2 (SARS-COV-2).
The nucleic acid sequence of SARS-COV-2 differs from known human coronavirus species (SARS and MERS). After comparison, the new coronavirus was found to be similar to some β-coronaviruses found in bats (Yin et al., 2018; National Health Office Medical Letter, 2020b). At present, the homology with BAT-sl-covzc45 exceeds 85%. (de Wit E et al., 2016). It was detected in patients' lung fluid, blood, and throat swab samples, and viruses isolated under an electron microscope were found to exhibit typical coronavirus characteristics. In order to better understand this new coronavirus, further research will be carried out as soon as possible with the goal of developing antiviral drugs and vaccines (Zumla et al., 2016).
Table 3
As of January 26, 2020, 2,036 patients have been diagnosed with COVID-19. Symptoms include fever (90%), discomfort, dry cough (80%), shortness of breath (20%), and respiratory distress (15%).
Host range and tissue tropism vary greatly among different coronaviruses. In general, thyroid coronavirus and β-coronavirus can infect mammals, and gamma coronavirus and triangular coronavirus can infect birds, but some of these viruses can also infect mammals (Cui et al., 2019; Woo et al., 2012). Before 2019, there were only six coronaviruses with the capability of infecting humans and causing respiratory diseases: (i) HCoV-229E, HCoV-OC43, HCoV-NL63, and HKU1, which can cause only mild upper respiratory diseases, and in very few cases can cause severe infections; and (ii) SARS-CoV and MERS-CoV in infants and the elderly can infect the lower respiratory tract and cause severe respiratory syndrome. (Fehr et al., 2015; Su et al., 2016) The new coronavirus SARS-COV-2 belongs to the β-coronavirus group, according to genomic analysis. It can also infect the lower respiratory tract and cause pneumonia, but the overall symptoms are milder than those of SARS and MERS (Table 4).
Table 4
In the study by Ji et al. (Ji et al., 2020), relative synonymous codon usage (RSCU) values were used for comprehensive sequence analysis and comparison of relative synonymous codons between different animal species. The results showed that 2019-nCoV appeared to be a recombinant virus between bat coronavirus and unknown coronaviruses.
At present, because there is no effective antiviral treatment for coronavirus, the main treatment method is supportive therapy. Ribavirin-containing recombinant interferon (IFN) has a limited effect on coronavirus infections (Cinatl et al., 2003). After the prevalence of SARS and MERS, many anti-CoV drugs for CoV protease, polymerase, methyltransferase, and entry proteins have been developed, but have not been confirmed in clinical trials. (Chan et al., 2013; Cheng et al., 2015; Wang et al., 2015)
Patients may have mental anxiety, and memory or cognitive impairment, which can be assessed by the Hospital Anxiety and Depression Scale (HADS), Mini-Mental State Examination (MMSE), and the Dream Anxiety Scale to explore the relationship between mental cognitive function and COVID-19 patients. SARS-COV-2 can be spread by viral contact with the lung tissue and conjunctiva, causing damage to the human body as well as anxiety, cardiovascular disease, and endocrine disease (Figure 5).
Figure 5
There are many vaccine strategies for CoV. Inactivated, attenuated, and live viruses, viral vector-based vaccines, subunit vaccines, recombinant proteins, and DNA vaccines have been developed, but thus far, only animals have been tested. (Graham et al., 2013) Currently, there is no effective treatment or vaccine, and therefore, the most efficient methods to manage SARS-COV-2 infection are to control the source of infection, early diagnosis, reporting, isolation, supportive treatment, and timely release of epidemic information to avoid unnecessary panic. For individuals, good personal hygiene, appropriate masks, ventilation, and avoiding crowded places will help to prevent SARS-COV-2 infection.
To more closely study this new virus, in 2019, we examined the data from 42 patients diagnosed in our hospital, analyzed their symptoms, signs, complications, and cytokines, and then reported the results. Through serological examination of COVID-19 patients, we found that patients exhibited a significant decrease in CD3, CD4, and CD8 compared with ordinary people, and the levels of CD3, CD4, and CD8 in severe patients were lower than those in common patients. We speculate that SARS-COV-2 and cellular immune response, and especially T cells, are closely related. 2019-nCoV may inhibit T cell function in the body, cause T cell dysfunction, and reduce the levels of CD3, CD4, and CD8. As the patient's immunity decreases and the greater the degree of decline, the more serious the patient's condition.
We also found that in the imaging examination of patients, there was no difference in the number of lesions in common patients compared with severe patients, and the average cumulative number of lung lobes was the same as that in severe patients. Therefore, it is unlikely that the number of lesions detected by imaging can be regarded as ordinary in common patients and severe patients.
Ultimately, we found that patients with blood type A accounted for 44.9% of all patients, which is significantly higher than patients with other blood types. We could not locate any previous studies that mentioned that patients with blood type A are more susceptible to SARS-COV-2. Therefore, we require a larger sample size to explore this inherent relationship.
Our study has some limitations. The limited number of cases when collecting samples led to a small number of samples, and some unknown variables may affect the experimental results. Most SARS-COV-2 patients are related to Wuhan. In addition to known variables (such as eating wild animals), there are also unpredictable variables, such as regional differences and customs differences, which may affect the experimental results.
Table 5