Descriptive Epidemiology of 12 Confirmed 2019-Novel Coronavirus (2019-nCoV) Cases in Japan (As of 3 February 2020)

(As of 2020/2/3)

On 3rd January, 2020, a cluster of severe pneumonia cases of unknown etiology or unknown cause in Wuhan City, Hubei Province was reported by China’s Ministry of Health. In response to this emerging infectious disease of unknown cause, Japan updated its disease surveillance system on 6th January, 2020 in order to capture suspected cases of pneumonia related to the outbreak originating in Wuhan City. This was done in accordance to the law: “Prevention of Infectious Diseases and Medical Care for Patients with Infectious Diseases Act”, Article 14, paragraph 1. The cause of severe pneumonia cases originating in Wuhan City, China was identified as novel coronavirus (2019-nCoV) and became a designated infectious disease in Japan on 1st February, 2020. For a case definition of 2019-nCoV used prior to its addition as a designated infectious disease, please refer to “Response to novel coronavirus-associated pneumonia reported in Wuhan, Hubei Province, China and measures against nosocomial infection (in Japanese) (”.

This document summarizes the 12 confirmed 2019-nCoV cases detected before 1st February, 2020 prior to the addition of 2019-nCoV as a designated infectious disease. This information was collected from relevant municipalities by the Ministry of Health, Labor and Welfare, as of 3rd February. In the future, some of the following information may be revised or updated.

Excluded from this summary are the eight cases detected among Japanese citizens who returned to Japan on charter flights from Wuhan City on 31st January, as these cases are still being monitored (as of 3rd February, 2020).

From 15th - 31st January, 2020, a total of 12 patients were lab-confirmed as cases of 2019-nCoV(as of 3rd February, 2020). Genetic testing of the specimens was performed at the National Institute of Infectious Diseases (NIID) or at the local public health institute(s) of relevant municipalities. The age distribution of the cases ranged from twenty to sixty-nine years old, with 2 cases in their twenties, 3 cases in their thirties, 5 cases in their forties, 1 case in their fifties, and 1 case in their sixties. The gender distribution was 50:50 with 6 males and 6 females. The onset date of symptoms of the cases ranged from 3rd to 26th January, 2020. (Figure.1)

Of the total 12 confirmed cases, six were imported from China with five cases directly from Wuhan city, and one from Hubei Province other than Wuhan City. Of the remaining six cases, there was one case from each of the following prefectures: Kanagawa, Nara, Osaka, Mie, Kyoto and Chiba. Nine out of 12 cases had a history of traveling to or staying in Wuhan within fourteen days of onset of symptoms, with the remaining three cases without recent history of traveling to China. Of the three cases without recent travel to China, two had business-related contact with a traveler from Wuhan City, with the remaining case having had business-related contact with a traveler from China other than Wuhan City, within fourteen days of onset of symptoms. This suggests a high possibility of human-to-human transmission of 2019-nCoV in Japan.

The symptoms for the confirmed cases at the time of reporting ranged from fever, cough, pneumonia, arthralgia, and sore throat as described in Table 1; with pneumonia seen in all 12 cases and fever in 11. As of 3rd February at 12pm, all 12 cases’ conditions had improved or become stable. Contact tracing and observation of close contacts was completed for one case on 24th January, 2020.


National Institute of Infectious Diseases

Copyright 1998 National Institute of Infectious Diseases, Japan