At the end of 2019, pneumonia caused by novel coronavirus 2019 (nCoV) emerged in Wuhan city, China. Many airline travelers moved between Wuhan and Japan at that time, suggesting that Japan is at high risk of invasion by the virus. Diagnostic systems for 2019-nCoV were developed with urgency. Two nested RT–PCR assays and two real-time RT–PCR assays were adapted to local Japanese conditions. As of 8 February 2020, the assays developed have successfully detected 25 positive cases of infection in Japan.