بیماری زایی و قابلیت انتقال ۲۰۱۹-nCoV
Abstract
1- Pathogenicity of 2019-nCoV
2- Transmissibility of 2019-nCoV
3- Relationship between viral pathogenicity and transmissibility
Declaration of Competing Interest
Acknowledgement
References
Abstract
A zoonotic coronavirus, tentatively labeled as 2019-nCoV by the World Health Organization (WHO), has been identified as the causative agent of the viral pneumonia outbreak in Wuhan, China, at the end of 2019. Although 2019-nCoV can cause a severe respiratory illness like SARS and MERS, evidence from clinics suggested that 2019-nCoV is generally less pathogenic than SARS-CoV, and much less than MERSCoV. The transmissibility of 2019-nCoV is still debated and needs to be further assessed. To avoid the 2019-nCoV outbreak turning into an epidemic or even a pandemic and to minimize the mortality rate, China activated emergency response procedures, but much remains to be learned about the features of the virus to refine the risk assessment and response. Here, the current knowledge in 2019-nCoV pathogenicity and transmissibility is summarized in comparison with several commonly known emerging viruses, and information urgently needed for a better control of the disease is highlighted.
Pathogenicity of 2019-nCoV
Of the first 41 cases of laboratory confirmed infections with 2019-nCoV, all had viral pneumonia and almost a third of the patients developed acute respiratory distress syndrome (ARDS) requiring intensive care and 6 patients (14.6%) died [6]. Since the fatality rate of the early reported case is often high due to bias towards more severe cases, the true mortality risk might be much lower. As of Jan 27, 2020, about 3000 cases have been confirmed in China, and cases were also reported in Japan, South Korea, Thailand, Singapore, the United States, and Australia, all of which were exported from China. The total number of deaths from the pneumonia-related disease accounts for less than 3%. In addition, most of those who have died had underlying health conditions such as hypertension, diabetes or cardiovascular disease that compromised their immune systems. Although the fatality rate will continue to change until all infected people recover, it appears that 2019-nCoV is less pathogenic than SARS-CoV (~10%), and much less than MERS-CoV (~40%).
Coronaviruses are a group of viruses that cause a significant percentage of all common colds in human adults and children. Four human coronavirus including 229E, OC43, NL63, and HKU1 are prevalent and typically cause common cold symptoms in immunocompetent individuals. SARS-CoV which causes SARS, has a unique pathogenesis because it causes both upper and lower respiratory tract infections. 2019-nCoV is classified as a novel betacoronavirus belonging to the sarbecovirus subgenus of Coronaviridae family. The genome sequence of 2019-nCoV is about 89% identical to bat SARS-like-CoVZXC21 and 82% identical to human SARS-CoV [7]. It has been reported that 2019-nCoV uses the same cell entry receptor, ACE2, to infect humans, as SARS-CoV [8], so clinical similarity between the two viruses could be expected, particularly in severe cases. Notably, there are signs, from what is still very limited data, that the clinical features of 2019-nCoV seem to be more variable.