IASR

ISSN 0915-5813

Vol. 41 No. 7 (No. 485) July 2020
Infectious Agents Surveillance Reporthttps://www.niid.go.jp/niid/en/iasr-e.html

Epidemiologic situation of COVID-19 overseas (as at 4 June 2020)..... 105
Epidemiology during the early stages of COVID-19 outbreak on the
Diamond Princess cruise ship in Japan............................................. 106
Cluster-based approach to COVID-19 response in Japan.................... 108
COVID-19 epidemic in Osaka Prefecture............................................. 110
Descriptive study of 4,109 confirmed cases of COVID-19 in Tokyo
Prefecture (as at 3 June 2020)............................................................ 111
Outbreak and nosocomial infection control of COVID-19 at core
hospitals in Tokyo Prefecture............................................................. 113
Experience in responding to a COVID-19 outbreak at a facility for thementally challenged in Chiba Prefecture.......................................... 114
TMPRSS2-expressing cells and isolation of respiratory viruses......... 115
Correlation between days of illness and real-time PCR Ct values..... 117
Analysis and histopathology of COVID-19 autopsy cases................... 118

National Institute of Infectious Diseases andTuberculosis and Infectious Diseases
Control Division,
Ministry of Health, Labour and Welfare

Evaluation of the COVID-19 epidemic in Nagoya City: importance ofthe number of tests, number of positive tests, positivity rate andstratification by test population......................................................... 119
Detection of SARS-CoV-2 in sewage...................................................... 122
Seasonality of human coronavirus (HCoV) infection – Report fromthe Infectious Agent Surveillance System (2015-2019).................... 124
Pertussis in Toyama Prefecture, 2019................................................... 125
Characteristics of the re-emergence of COVID-19 in Sapporo City
after April 2020................................................................................... 127
Transmission of SARS-CoV-2 among medical workers at a core
hospital in Sapporo City..................................................................... 129
Characteristics of a COVID-19 outbreak at a social welfare facility
for the elderly in Sapporo City........................................................... 130
COVID-19 outbreak at a medical and nursing care hospital in Osaka Prefecture– Nosocomial transmission, countermeasures and its effects –....... 131<THE TOPIC OF THIS MONTH>
COVID-19 as of May 2020
Coronaviruses are enveloped, positive-sense single-stranded RNA viruses. Coronaviruses known to infect humans include fourcausative viruses of the common cold, human coronavirus 229E, OC43, NL63, and HKU1, and severe acute respiratory syndrome (SARS)
coronavirus (SARS-CoV) and Middle East respiratory syndrome (MERS) coronavirus (MERS-CoV), both of which cause severe pneumonia.
SARS-CoV-2, the cause of coronavirus disease 2019 (COVID-19), which was first identified in December 2019, is classified in the same
Betacoronavirus genus as SARS-CoV with high genetic homology (approximately 80%), and was reported to bind and enter human cells
using the receptor ACE2.
Domestic and International Trends:
On December 31, 2019, COVID-19 was reported to the World Health Organization (WHO) from Wuhan City, Hubei Province of China,
as a cluster (a group with associations found among patients) of pneumonia cases of unknown etiology (p.105 of this issue). In response to
the increasing number of cases in China and confirmed human-to-human transmissions in 19 countries, including Japan, the WHO
declared on January 30, 2020 that COVID-19 is a “public health emergency of international concern (PHEIC)” under the International
Health Regulations (IHR). Due to the subsequent spread of infection, the WHO declared COVID-19 a “pandemic” on March 11, 2020. As
at June 4, 6,287,771 cases were confirmed in 216 countries in all 6 WHO regions and there were 379,941 deaths (p.105 of this issue). As
at 24:00 on May 31, according to the press release of the Ministry of Health, Labour and Welfare (https://www.mhlw.go.jp/stf/seisakunitsuite/bunya/0000121431_00086.html), the domestic number of cases with positive PCR tests was 16,884 (16,679 domestic cases, 15 returnees bycharter flights, and 190 cases at airport quarantine) (not including those quarantined or isolated onboard the cruise ship “Diamond
Princess” (p.106 of this issue)). Of these, 892 deaths were identified, which included the results from a follow-up survey.
In Japan, the legislation to classify COVID-19 as a designated infectious disease was issued on January 28 and implemented on
February 1 (Table 1). Among the cases reported to the National Epidemiological Surveillance of Infectious Diseases (NESID) since then,
16,911 cases were tested and confirmed by the local governments (15,012 case-patients, 1,868 asymptomatic virus carriers, and 31 deaths
at the time of notification) as at the 22nd week of 2020. As at May 31, the largest number of cases reported to NESID was on April 9 (655cases), while the largest number of cases by onset day was April 1 (431 cases, only cases with known onset date) (Figure in p.105). There
were 9,284 males and 7,627 females (male/female ratio 1.2:1), and the median age was 49 years (range 0-104). The main symptoms at thetime of reporting were fever (75%), cough (43%), acute respiratory tract symptoms other than cough (8.9%), and severe pneumonia (6.9%).
In Japan, from early March, the number of cases suspected to be associated mainly with Europe and the United States increased. By midMarch, the number and percentage of cases with unknown sources of infection increased. By late March, clusters were reported mainly inurban areas (pp.110 & 111 of this issue). Of the pathogens identified from suspected COVID-19 cases reported to NESID’s Infectious
Agents Surveillance System from public health institutes and local public health centers nationwide from January 29 to June 16, 3,177
were SARS-CoV-2 (2,188 in April) and 24,555 were negative (Table 2 in p.105).
Transmission Route, Treatment, and Prevention:
The initial symptoms of COVID-19 are similar to those of influenza or the common cold, and it is difficult to distinguish them in theearly stage of the disease. The primary transmission route is droplet infection and through direct contact. After an incubation period of
1-14 days (5-6 days is the most frequent according to the WHO, as at April 17), patients develop symptoms such as fever, respiratory tract
symptoms, and general fatigue. The majority of patients (approximately 80% according to the WHO) recover without the need for
hospitalization. Common cold-like symptoms often persist for approximately one week, and from around this time on, pneumonia may bediagnosed by chest radiography and computed tomography. Some patients may progress to a critical condition and develop respiratory
failure. The elderly and those with underlying health conditions are particularly at high risk of developing a severe outcome.
Table 1. Management of COVID-19 patients in Japan
Infectious Diseases Control Law (implemented on 1 February 2020)
As a designated infectious diseases, physicians who diagnose patients with COVID-19 must immediately notify the cases to their prefectural
governors via local public health centers.
School Health and Safety Act (notification on 28 January 2020)
When COVID-19 is designated as a designated infectious disease according to this government ordinance, it is considered to be a Type I
infectious disease. The principal may suspend the attendance of any child or student who has contracted the disease until he/she is cured.

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（Continued on page 104′）IASR Vol. 41 No. 7（Jul. 2020） 2′（104′）（THE TOPIC OF THIS MONTH-Continued）
Effective and specific treatments for COVID-19 have yet to be established. Remdesivir, which was developed for the treatment of
Ebola hemorrhagic fever, received special approval on May 7, and as at June 17, drugs, such as favipiravir and ciclesonide, are evaluatedunder observational studies, specific clinical studies, and corporate trials in Japan. Vaccines to prevent COVID-19 are being developed andevaluated in many countries, including Japan.
Tests, Diagnosis, and Pathological Findings:
The National Institute of Infectious Diseases (NIID) developed a real-time PCR test to detect the SARS-CoV-2 gene and published alaboratory manual for government laboratories on tests for detecting the novel coronavirus pathogen (https://www.niid.go.jp/niid/ja/
diseases/ka/corona-virus/2019-ncov/2518-lab/9403-labo-manual.html). NIID provides support to laboratory facilities, such as public healthinstitutes, that conduct diagnostic tests for local governments, administers the distribution of SARS-CoV-2, classified as a class 4 pathogen
designated under the Infectious Diseases Control Law, and develops cell culture for efficient isolation of SARS-CoV-2 (p.115 of this issue).
The correlation between the number of ill days and the threshold cycle (Ct) values of real-time PCR testing has been used to inform clinicaldecisions (p.117 of this issue).
As for SARS-CoV-2 antigen testing, a rapid immunochromatography diagnostic kit based on enzyme immunoassay is in use and can
detect patients who secrete large amounts of the virus. A rapid testing kit for the SARS-CoV-2 antibody is available. However, results
should be interpreted with caution because the evaluation of its performance is not sufficient. It is also necessary to prepare reference
panels for the quantitative measurement of antibody titers.
The analysis of the histopathology of COVID-19 autopsy cases is highly important to elucidate the pathology of the disease. In thefirst autopsy case in Japan, the lungs exhibited diffuse alveolus injury, a pathological finding of acute respiratory distress syndrome. The
largest amount of SARS-CoV-2 virus detected was from the peripheral tissue of the lungs, followed by the bronchus, trachea, andnasopharynx. Low copy numbers of virus genes were also detected from blood and stool specimens (p.119 of this issue).
Public Health Countermeasures, Declaration of the State of Emergency, and its Subsequent Lifting:
On March 14, the partial revision of the National Action Plan for Pandemic Influenza and New Infectious Diseases was officiallyapproved by the Cabinet, and COVID-19 became regarded as Pandemic Influenza and New Infectious Diseases enacted by the law. On
March 28, the basic policy for COVID-19 was announced: it emphasized controlling the number of cases, and maintaining medical systems
and social functions, promoting the containment of cluster events by active epidemiological investigations. It is a characteristic of
COVID-19 that clusters form quickly when an infected person comes in contact with susceptible persons in settings that fulfill the 3 Cs
(closed spaces, crowded places, and close-contact settings). It is important to identify these clusters and interrupt their chains oftransmission (p.108 in this issue). In Japan, public health centers are conducting contact tracing, including identification of movement
histories of infected persons, listing of close contacts, and monitoring health conditions (pp.113 & 114 in this issue).
As the number of cases with unknown routes of transmission was increasing and the medical system was at risk of being overwhelmed,
a state of emergency was declared in 7 prefectures on April 7, and then nationwide on April 16. After the situation improved, the state of
emergency was lifted in all prefectures on May 25.
Future Agenda:
Measures led by the Ministry of Health, Labour and Welfare are to publicize information needed to control infection, support the
medical system, and promote research and development.
As for the information collection system, the Health Center Real-time Information-sharing System on COVID-19 (HER-SYS) was
introduced to share and collect information. This system aimed to reduce the workload of public health center and simultaneously enables
more rapid collection of information. Using HER-SYS, information can be shared immediately among public health centers, local
municipalities (other than public health centers), and medical facilities. Furthermore, the COVID-19 Contact-Confirming Application/app(COCOA) was developed to enable each person to identify contacts quickly. Upon consent of the user, this app uses the Bluetooth functionof the user’s smartphone, and after the privacy of both the infected person and the contact person are ensured, the user can be notified
when the user may have come in contact with an infected user. The notified users can receive support from the public health center, suchas prompt testing, which is expected to prevent the spread of the virus. In this manner, in addition to rapid collection and sharing of
information, and enabling changes in behavior such as social distancing, an approach that ensures that contacts can promptly consult
medical facilities is being promoted.
As for the medical system, in addition to continuing border protection measures at ports and airports, and by actively testing those
who have been in close contact with infected persons, early detection of infected individuals, including asymptomatic cases, and effective
countermeasures against clusters, will be implemented. In addition to nasopharyngeal swab PCR testing, the following diagnostic tests
have been put into practical use: PCR testing using saliva specimens, rapid antigen test using nasopharyngeal swabs, and quantitative
antigen test using nasopharyngeal and saliva specimens. These tests are being implemented accordingly, based on the current capacity
and state of the infection prevention measures at the testing facilities. It is important to establish a consultation system, such as one where
the testing facilities cooperate with the medical association, and a system that includes care facilities tailored to accommodate the casepatients’ specific symptoms, to prevent the medical system from collapsing.
Regarding research and development, the development of drugs in addition to remdesivir are being promoted, along with thedevelopment of vaccines both in Japan and overseas, in an all-out effort to realize their real-world application.

The statistics in this report are based on 1) the data concerning patients and laboratory findings obtained by the National Epidemiological
Surveillance of Infectious Diseases undertaken in compliance with the Act on the Prevention of Infectious Diseases and Medical Care for Patientswith Infectious Diseases, and 2) other data covering various aspects of infectious diseases. The prefectural and municipal health centers andpublic health institutes (PHIs), the Department of Environmental Health and Food Safety, the Ministry of Health, Labour and Welfare, andquarantine stations, have provided the above data.

Infectious Disease Surveillance Center, National Institute of Infectious Diseases
Toyama 1-23-1, Shinjuku-ku, Tokyo 162-8640, JAPAN Tel (+81-3)5285-1111

病原微生物検出情報 Vol. 41 No. 7（2020. 7） 3 （105）
図. 届出日別, 発症日別 COVID-19 届出数，2020年 1 月14日〜 5 月31日
Figure. Daily number of notified COVID-19 cases, 14 January - 31 May 2020, Japan

届出数

No. notified cases

700
600
500

（a）届出日n=16,911

Date of notification

400
300
200
100
0

届出数

No. notified cases

700
600
500

14 17 20 23 26 29 1 4 7 10 13 16 19 22 25 28 2 5 8 11 14 17 20 23 26 29 1 4 7 10 13 16 19 22 25 28 1 4 7 10 13 16 19 22 25 28 31

1月 January

2月 February（b）発症日n=10,572

3月 March

4月 April

5月 MayDate of onset

400
300
200
100
0

14 17 20 23 26 29 1 4 7 10 13 16 19 22 25 28 2 5 8 11 14 17 20 23 26 29 1 4 7 10 13 16 19 22 25 28 1 4 7 10 13 16 19 22 25 28 31

1月 January

2月 February

3月 March
4月 April
5月 May（感染症発生動向調査：2020年 6 月 3 日現在届出数）（National Epidemiological Surveillance of Infectious Diseases: as at 3 June 2020）

表 2. 新型コロナウイルス感染症疑い例から検出された病原体, 2020年 1 月〜 6 月 (n=27,896)
Table 2. Reported number of pathogens isolated/detected (n) from COVID-19-suspected cases, January-June, 2020 (n=27,896)
病原体 Pathogen
Negative
SARS-CoV-2
Human coronavirus 229E
Human coronavirus HKU1
Human coronavirus NL63
Human coronavirus OC43
Influenza virus AH1pdm09
Influenza virus B
Parainfluenza virus
Respiratory syncytial virus
Human metapneumovirus
Rhinovirus
Coxsackievirus B5Enterovirus 68
Adenovirus
Herpes simplex virus 1
Human bocavirus
Mycoplasma pneumoniae
Total

January
34
2
−
−
−
−
−
2
−
−
−
−
−
1
−
−
−
−
39

検体採取月
February
1,725
181
4
2
2
9
4
−
2
7
18
13
2
−
5
1
1
2
1,978

Month of specimen collection
March
April
May
6,913
11,627
3,881
541
2,188
232
15
−
−
8
−
−
−
−
−
22
−
−
1
−
−
3
−
−
1
−
−
6
−
−
19
−
−
12
−
−
−
−
−
−
−
−
−
−
−
2
−
−
−
−
−
−
−
−
7,543
13,815
4,113

June (-15th)
375
33
−
−
−
−
−
−
−
−
−
−
−
−
−
−
−
−
408

Total
24,555
3,177
19
10
2
31
5
5
3
13
37
25
2
1
5
3
1
2
27,896(病原微生物検出情報：地方衛生研究所、保健所からの報告、2020年 6 月16日現在)(Infectious Agents Surveillance System: Data based on reports from public health institutes and public health centers as at 16 June 2020)