A novel coronavirus, officially termed as severe acute respiratory syndrome (SARS)-CoV-2, emerged in Wuhan, China, toward the end of 2019. Just four months later, more than 100,000 people were diagnosed with COVID-19, the resulting disease. The genetic analysis of SARS-CoV-2 revealed that this virus is a new Betacoronavirus, closely related to bat-derived SARS-like coronaviruses. Clinical data from hospitals in China have revealed that approximately 10% of the infected patients have severe disease requiring intensive care. Since containment of the outbreak may have partially failed due to asymptomatic transmission, it is imperative to accelerate the development of rapid point-of-care diagnostic tests, vaccines, and therapeutics for the COVID-19 epidemic.

A novel coronavirus — officially named as severe acute respiratory syndrome (SARS)-CoV-2 by the authorities — emerged in Wuhan, China, toward the end of 2019 [1, 2]. Just four months later, more than 100,000 cases have been diagnosed with the resulting disease, COVID-19, in more than 100 countries at the time of writing this paper [3]. Not only does mainland China have the most number of reported cases (94.4%), but its case-fatality rate is also relatively higher than that of other countries as of February 28, 2020 (China: 3.5%, 2,791 deaths among 78,961 confirmed cases; other countries: 1.4%, 67 deaths among 4,691 confirmed cases) [4]. In an attempt to restrict the outbreak, China quickly implemented an unprecedented measure of quarantining 35 million people in Wuhan and several other cities, but its impact on slowing the global spread of the virus now seems inadequate. In fact, the number of cases in local human-to-human transmission kept soaring in several countries as of March 25, 2020: Italy 63,927 cases, United States of America 42,164 cases, and Spain 33,089 cases [3]. In Japan, 1,128 cases were confirmed based on positive viral nucleic acid test results, and the overall case-fatality rate was 3.7% (i.e., 42 deaths) [3].