Concluding remarks and future perspectives
The outbreak of SARS-CoV-2 provides an unprecedented opportunity for us to keep track of a zoonotic CoV that has just crossed the species barrier to infect humans. Whether the transmission of SARS-CoV-2 within humans will come to a dead end depends primarily on whether the virus has acquired the ability to transmit from person-to-person efficiently and sustainably. In the cases of MERS-CoV and SARS-CoV, secondary and tertiary spreading becomes weakened, giving the opportunity for quarantine and other measures of human intervention to take effect so that human-to-human transmission cannot be sustained. However, if transmissibility of SARS-CoV-2 is comparable to that of the other four community-acquired HCoVs and influenza viruses, we should prepare well for the arrival of another community-acquired HCoV. In this regard, it is crucial to determine the infection rate in the epicentre of Wuhan by RT–PCR and serology. The real ratios of asymptomatic carriers and patients with mild symptoms as well as the transmission rates in secondary, tertiary, and quaternary spreading are also pivotal. If the attack rate is sufficiently high, it will be tremendously challenging to contain the spreading before herd immunity develops.
The virulence and pathogenicity of SARS-CoV-2 seem to lie between those of SARS-CoV and community-acquired HCoVs. If SARS-CoV-2 becomes more attenuated as it adapts well in humans and increases its person-to-person transmissibility as anticipated, similar strategies for prevention and control of CoVs and influenza viruses might be adopted. To reduce morbidity and mortality caused by SARS-CoV-2, vaccines could be developed. If quarantine cannot contain the spreading and if it is necessary, vaccination will provide the second opportunity to eradicate SARS-CoV-2 from humans.
The interplay between SARS-CoV-2 and host antiviral defence is at the core of viral pathogenesis. It also determines the infection outcome and might explain the existence and risk of asymptomatic carriers. SARS-CoV-2 is very similar to SARS-CoV in many aspects. Lessons from other human pathogenic viruses including SARS-CoV, community-acquired HCoVs, influenza viruses, and HIVs are very enlightening and helpful. However, SARS-CoV-2 is also a novel human pathogen that may interact with host antiviral defence in a unique manner. Basic research in the field of SARS-CoV-2-host interaction holds the key to many important questions in disease control and prevention. Many important questions concerning the identity and mechanisms of interferon antagonists encoded by SARS-CoV-2 will be answered in the months and years to come. Particularly, comparative analyses of SARS-CoV-2 and SARS-CoV will advance the understanding of SARS-CoV-2 pathogenesis. The new knowledge gained will guide the development of vaccines and anti-SARS-CoV-2 therapeutics.