Case of First Human-to-Human Infection of Novel Coronavirus in Japan

The novel coronavirus (hereinafter, SARS-CoV-2) is a new type of coronavirus that has been detected in patients with pneumonia of unknown cause, which has occurred in Wuhan City, Hubei Province in the People's Republic of China since December 2019. On February 11, the World Health Organization (WHO) specified the official name for the novel coronavirus infection as “COVID-19 (coronavirus disease 2019)” (hereinafter referred to as “COVID-19”). This paper summarizes and reports the results of an active epidemiological surveillance forcases of human-to-human infection of COVID-19 in 3 persons with no travel history to Wuhan for 2 weeks before the onset of the disease, in cooperation with local governments.

The first person without a travel history to Wuhan in Japan (Patient 1) is a man in his 60s. He developed a chill, cough, and arthralgia on January X (Day X). On Day (X + 3), Patient 1 visited a medical institution and was followed up without abnormalities in various tests. However, as the symptoms became exacerbated, he visited the medical institution again on Day (X + 11). A chest X-ray showed a finding of pneumonia and he was hospitalized. The patient was in contact with tourists on a tour from Wuhan City (Figure) in the course of his business. COVID-19 was suspected and a test was conducted. He was found to be SARS-CoV-2 positive on Day (X + 14).

Patient 2 was a woman in her 40s who had been in contact with Patient 1 and tourists from Wuhan City from Day (X - 2) to (X + 2) (Figure). On Day (X + 6), Patient 2 developed pyrexia, cough, sputum, etc., and visited a medical institution on the same day, and days (X + 7), (X + 8), and (X + 9). On Day (X + 9), chest CT images showed a finding of bilateral pneumonia, and she was hospitalized. The health center received a notification regarding the conduct of surveillance for suspected disease on Day (X + 13) and submitted it as an administrative test. In addition, Patient 2 was found to be a person who had been in contact with Patient 1 on Day (X + 14); the test on Day (X + 15) showed a SARS-CoV-2 positive result. Patient 3 is a woman in her 20s. She developed cough and nasal discharge on Day (X + 6), and visited a medical institution on Days (X + 15) and (X + 16). Patient 3 was found to be a person who had been in contact with Patient 1 on Day (X + 16) (Figure). A test showed a SARS-CoV-2 positive result on Day (X + 17), and she was hospitalized on Day (X + 18); chest CT images showed a finding of pneumonia. Patients 1 and 2 were together in Tour (ii), and Patient 1 and Patient 3 were together in Tour (iii); however, the contact was only during a conversation regarding administrative matters (Figure). Also, the participants in Tours (i) and (ii) were from Wuhan city, and Patients 2 and 3 sat on seats behind that of Patient 1. Patient 1 basically wore a mask after the onset, during work at times other than meals. Patients 1-3 also had no memory that any of the tourists from Tours (i)-(iv) had exhibited symptoms of upper respiratory tract inflammation.

Although the source of infection could not be identified based on these courses, it was inferred to be human-to-human infection that occurred among persons who shared the same space in Japan. In that case, the incubation period in this case was considered to be 3-8 days. In addition, because multiple local governments were involved in tracing those persons who were in contact with an infected person, and the information on the history of contact among Patients 1-3 led to the diagnosis of COVID-19, this was an example where the importance of prompt information sharing among relevant organizations and departments was again recognized.

We would like to express our deep appreciation to the medical institutions, health centers, public health institutes, and local governments for their cooperation.