IASR

ISSN 0915-5813

Vol. 41 No. 4 (No. 482) April 2020
Infectious Agents Surveillance Reporthttps://www.niid.go.jp/niid/en/iasr-e.html

Measles outbreak stemming from a workshop of a religiousorganization, Mie Prefecture, January 2019....................................... 56
Summary and response of measles outbreak that occurred in a largecommercial facility in Osaka, February 2019...................................... 57
Measles seroprevalence in Japan FY 2019 - National Epidemiological
Surveillance of Vaccine Preventable Diseases (preliminary data)..... 58
Global situation of measles, 2019............................................................ 59

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

Japan International Cooperation Agency (JICA), Japan Disaster Relief(JDR) Infectious Diseases Response Team - Activity report of emergency
medical support for measles outbreak in the Independent State of
Samoa, 2019.......................................................................................... 61
The first human-to-human transmission case of severe acuterespiratory syndrome coronavirus 2 (SARS-CoV-2) in Japan............. 63<THE TOPIC OF THIS MONTH>
Measles in Japan, as of February 2020
Figure 1. Weekly number of notified measles cases, 2010-2019, Japan

No. notified cases

55
50
45
40
35
30
25
20
15
10
5
0
1 14 27 40

1 14 27 40

2010

2011

1 14 27 40 1 14 27 40

2012

2013

1 14 27 40

1 14 27 40

1 14 27 40

1 14 27 40

1 14 27 40

2014

2015

2016

2017

2018

1 14 27 40 Week ofdiagnosis

2019

Year

(National Epidemiological Surveillance of Infectious Diseases: as of 27 February 2020)

Measles is an acute viral disease caused by the measles virus, characterized by fever, rash, and catarrh. The measles virus istransmitted by aerosol, droplets, or contact infection, and is highly contagious. The incubation period is 10-12 days, and the infectious
period of the virus is from 1 day before onset to 3 days after the fever has subsided. There are few subclinical infections. Before theintroduction of the measles vaccine (before 1965), most people were infected by the age of 15. However, due to the improvement ofvaccination coverage, the number of measles cases has decreased and been ranging from tens to hundreds in recent years. In addition,
many patients are over 20 years old.
As the measles virus infects immune cells, the host becomes acutely immunocompromised, resulting in complications such as
otitis media, enteritis, encephalitis, and pneumonia. Those who develop pneumonia and encephalitis may die. It has also beenreported that the measles virus damages the host’s immune memory cells, impairing immunity to other infectious diseases acquiredin the past, and making the host more susceptible to reinfection with those infectious diseases. Although it is rare, patients may
develop encephalitis with a poor prognosis known as subacute sclerosing panencephalitis (SSPE). In addition, measles infection
during pregnancy can cause stillbirth or miscarriage. The World Health Organization (WHO) estimates that more than 140,000
persons, mainly children in developing countries, died from measles in 2018 (https://www.who.int/news-room/detail/05-12-2019-morethan-140-000-die-from-measles-as-cases-surge-worldwide).
On the other hand, measles is considered to be an infectious disease that can be eliminated because there is an excellent live
attenuated vaccine. In 2005, the WHO Western Pacific Region (WPR), to which Japan belongs, resolved to eliminate measles from theregion by 2012. In response to this, in Japan, a two-dose measles vaccination schedule (the 1st dose: 1-year-old children, the 2nd dose:children during the year before elementary school entry) was introduced in 2006 instead of a single-dose vaccination schedule.
However, due to the outbreak of measles among teens in 2007, the Ministry of Health, Labour and Welfare (MHLW) issued the“Guidelines for the Prevention of Specific Infectious Diseases: Measles” (hereinafter referred to as the guidelines) at the end of 2007
and took countermeasures, including implementation of the catch-up immunization program for age groups corresponding to the 1styear of junior high school (3rd dose) and the 3rd year of high school (4th dose) for 5 years (from 2008 to 2012) as a routine vaccination inorder to boost the immunity against measles among teens who had no opportunity for a second dose of the measles vaccine. As aresult, the number of measles patients has decreased since 2009, and the Regional Verification Committee of the WHO WPR verified
in March 2015 that Japan had eliminated measles and this status has been maintained to date.
Measles notifications under the National Epidemiological Surveillance of Infectious Diseases (NESID) system
Measles is a category V infectious disease according to the “Act on the Prevention of Infectious Diseases and Medical Care forPatients with Infectious Diseases” (referred to as the Infectious Diseases Control Law) (for the notification criteria and diseaseclassification, see: http://www.niid.go.jp/niid/images/iasr/35/410/de4101.pdf). The annual number of notified measles cases in Japanwas 11,013 in 2008 when measles became a notifiable disease, but it has markedly decreased since 2009.
In 2019, 745 cases of measles, the highest number of cases since 2009, were notified (Fig. 1). They included outbreaks, such as an
outbreak in an organization that emphasizes life independent of medicine, including vaccines, which spread to 8 prefectures with 74
cases (see p. 56 of this issue), and an outbreak that spread mainly in large commercial facilities (see p.57 of this issue). An emergency
school closure due to measles (week 22) was reported to the measles outbreak investigation by the facility (https://www.niid.go.jp/niid//
images/idsc/disease/measles/2019pdf/measschool19_20_03.pdf).

1′（ 53′）（Continued on page 54′）

IASR Vol. 41 No. 4（Apr. 2020） 2′（ 54′）（THE TOPIC OF THIS MONTH-Continued）
In terms of disease classification, 539 cases (laboratory- Figure 3. Reporting status of measles virus information by PHIs to
the Infectious Agents Surveillance System, 2008-2019, Japan
confirmed cases: 520 and clinically-diagnosed cases: 19, 72.3% of
10
20
30
40
50
60
70
80
90
100 ％
the total 745 measles cases) had all three main symptoms ofYear 02008
measles (fever, rash, and catarrh), and the number of modified
Proportion of measles cases with virus information(n=11,013)
reported to the Infectious Agents Surveillance System
2009
measles cases that were atypical with only one or two(excluding vaccine strain)(n=732)
2010
Proportion of measles cases with virus information
manifestation and laboratory-confirmed, was 206 (27.7% of the(n=447)
including nucleotide sequence data reported to2011
the Infectious Agents Surveillance System
total 745 measles cases).
(n=439)(excluding vaccine strain)
2012
Regarding the age distribution, patients over 20 years old(n=283)2013
accounted for 70.2% of all patients (523 / 745) (Fig. 2 in p.55).
(n=229)2014
Among the cases notified in 2019 (n=745), 195 (26.2%) were(n=462)2015
in unvaccinated individuals, among whom 36 were infants <1 of(n=35)
2016
age (18.5% of unvaccinated individuals) who had not reached(n=165)2017
the age for routine vaccination. There were 161 (21.6%) who(n=186)2018
received one dose, 104 (14.0%) who received two doses, and 285(n=279)2019(38.3%) with unknown vaccination history (Table 1 in p.55).
(n=745)n=No. notified cases
Current practice regarding laboratory diagnosis(Infectious Agents Surveillance System: as of 17 February 2020)
In principle, the guidelines revised in 2012 require the(National Epidemiological Surveillance of Infectious Diseases: as of 27 February 2020)
implementation of both IgM antibody test and virus-specific
RNA detection test (real-time RT-PCR) for all clinically-diagnosed measles cases. The IgM antibody tests are conducted at private
laboratories, and the virus-specific RNA detection tests are mainly carried out at the Prefecture and Municipal Public Health Institutes(PHIs). In 2019, 726 (97.4%) of 745 measles cases were notified as laboratory-confirmed cases. In order to demonstrate that Japan
has maintained the measles elimination status, it is necessary to confirm the absence of endemic measles virus transmission for morethan 12 months in Japan. Nucleotide sequence analysis of the region for genotyping of the measles virus (450 nucleotides) is required
to confirm the links in outbreaks and to distinguish whether the cases are imported.
Detection of measles virus (Infectious Agents Surveillance System)
In 2019, there were 640 cases, 616 excluding the vaccine strains (82.7% of the total 745 cases), in which the virus genome was
detected at PHIs and reported to the Infectious Agents Surveillance System, NESID’s laboratory surveillance system. Among these616 cases, the genotype of the virus was analyzed in 576 (77.3% of the total 745 cases), and the nucleotide sequence of the region
required for genotyping (450 nucleotides) of the measles virus was also reported in 400 cases (53.7% of the total 745 cases) (including
reports by the accession number of the gene banks and excluding the incomplete 7 sequences) (Fig. 3). The breakdown of the reported
genotype of the virus was as follows: 402 cases of genotype D8, 174 cases of genotype B3, and 40 cases of “not typed.” Among thereported cases with genotype information, 107 were in individuals who had traveled abroad before onset. For individuals withgenotype D8 viruses (65 cases in total), the countries of stay were Vietnam (29 cases), Thailand (14 cases), Myanmar (5 cases), Republicof Maldives (5 cases), etc., and those with genotype B3 viruses (38 cases in total) went to the Philippines (31 cases), Hong Kong (4cases), China (2 cases), etc. (including cases who visited two or more countries) (Table 2 in p.55).
Vaccination coverage
Since fiscal year (FY) 2006, 2-dose vaccination (the 1st dose and the 2nd dose) using the MR vaccine was introduced into the routine
immunization program and is still ongoing. In FY2018, the vaccination coverage was the highest ever, with 98.5% for the 1st dose and94.6% for the 2nd dose. The coverage of the 1st dose exceeded the target of 95% not only overall (for 9 consecutive years), but also ineach prefecture. The coverage for the 2nd dose exceeded 90% for 11 consecutive years, but was slightly short of 95% (https://www.niid.
go.jp/niid/images/idsc/disease/measles/2018-mr-pdf/2018_0-1_1.pdf).
National Epidemiological Surveillance of Vaccine Preventable Diseases (NESVPD)In FY2019, the NESVPD measles seroprevalence survey was conducted at the PHIs in 24 prefectures by measuring the measles
gelatin particle agglutination (PA) antibody titer (n=6,628) (see p. 58 of this issue). In principle, the blood collection period ran from
July 2019 to September 2019. The proportion of antibodies with a measles PA antibody titer of ≥16 has been ≥95% for all age groups≥2 years since FY2014 (Fig. 4 in p.55).
Further measures to be taken
Measles is a highly contagious disease with marked mortality. Although many measures towards measles elimination have been
implemented worldwide, it is still epidemic in many countries (see p. 59 of this issue). Now that traffic between Japan and overseas
is frequent, and it is difficult to prevent the entry of the measles virus from abroad, it is essential to prepare an environment in which
infection does not spread even if brought in. To this end, the following are required: 1) maintain the vaccination coverage of 2 doses ofroutine vaccination at 95% or higher and maintain a high antibody positivity level among the general population: 2) further strengthen
surveillance in order for patients to be detected early and appropriate measures can be taken to prevent the further spread of
infection: 3) recommend vaccination as necessary to those who have a high risk of infection, including healthcare workers, childwelfare facility staff, school officials, overseas travelers, and those who work at places with opportunities to be in contact withunspecified people such as airports. Moreover, it is necessary to collaborate with international organizations to provide international
cooperation to countries with an insufficient medical environment (see p. 61 of this issue). In addition, it is also important to offer
education and reliable information to promote the understanding of the benefits of vaccines in response to reluctance or refusal toreceive available vaccines (referred to as “vaccine hesitancy”), one of the public health threats listed by WHO in 2019.
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. 4（2020. 4） 3 （ 55 ）（特集つづき）（THE TOPIC OF THIS MONTH-Continued）
図 2. 麻疹患者の年齢分布，2008〜2019年
Figure 2. Age distribution of notified measles cases, 2008-2019, Japan
年 0％
Year

10

20

30

40

50

60

70

80

届出数

90

100 No. notified
cases

2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019

11,013
732
447
439
283
229
462
35
165
186
279
745
0

1-4

5-9 10-14

15-19

20-29

30-39

年齢群

40-49

50-59

60

Age group (year)（感染症発生動向調査：2020年2月27日現在届出数）(National Epidemiological Surveillance of Infectious Diseases: as of 27 February 2020)

表1. 麻疹患者の予防接種歴別届出数, 2008〜2019年
Table 1. Yearly number of notified measles cases by vaccination status, 2008-2019, Japan
年
Year

接種歴なし
Not vaccinated

1回接種
1 dose of MCV*

2回接種
2 doses of MCV*

接種歴不明
Unknown

患者届出数
No. notified cases

2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019

4,914 (590)
173 (73)108 (29)130 (25)79 (15)52 (11)216 (43)
16 (3)
47 (7)
33 (3)
63 (16)195 (36)

2,933 (12)
349
193
139
76
50
87 (3)
640
46 (1)
56 (2)
161 (1)

132
31
29
26
17
9
32
0
25
21
43
104

3,034 (9)179 (1)
117
144
111
118
127
13
53 (1)
86
117
285

11,013 (611)732 (74)447 (29)439 (25)283 (15)229 (11)462 (46)
35 (3)
165 (8)186 (4)279 (18)745 (37)（ ）内は0 歳再掲（感染症発生動向調査：2020年2月27日現在届出数）
No. notified cases < 1 year of age indicated in parenthesis *Measles-containing vaccine(National Epidemiological Surveillance of Infectious Diseases: as of 27 February 2020)

Hong Kong*

Maldives*

Vietnam*1
1-

Thailand*1
1-

India*

Nepal*

1
1

China*

Laos*

Total
616 408 65 13 136 509 107 6 1 2 1 2 32 1 1 1 1 2 1 1 1 1 2 1
not typed
1 1
7
36 4 140
32 1
B3- 31 1
1
1
174 137 13
1 24 136 38 D8
2
2
- 2
2
1
402 239 51 12 105 337 65 5
1
1
1
1
1
1
†Including multiple situations. *Including cases who has visited two or more countries (e.g. Thailand / Vietnam)[Infectious Agents Surveillance System: as of 28 February 2020 from prefectural and municipal public health institutes (PHIs)]

Qatar*

Sri Lanka

New Caledonia

UK

USA

Germany

Singapore

TurkeyUkraineBrazilCanadaPhilippines

Bangladesh

Korea

Cambodia

Malaysia

Italy

Destination abroad*

MyanmarTravel history abroad

Outbreak

Local

Familial

Sporadic

Genotype

No. of cases

Epidemiologicalsituation†

No/unknown travel
history

Table 2. Measles virus isolation / detection by epidemiological situation, travel history and destination abroad, 2019

1
1
-

3
2
1

15
1
14

5
4
1

5
5

29
29

図 4. 年齢別／年齢群別麻疹抗体保有状況，2019年度
Figure 4. Proportion of seropositive against measles virus by age and vaccination status, fiscal year 2019, Japan

ＰＡ抗体陽性者の割合(≥1:16)

Proportion PA-antibody positive (>1:16)

100

％

抗体陰性者

90

(n=243)80

抗体陽性者（ワクチン接種歴別）

70
60
50

(n=243)

Antibody-positiveby vaccination status

有 1回接種 (n=1,525)

1 dose of MCV＊ (n=1,525)

有 2回接種 (n=1,324)

2 doses of MCV ＊ (n=1,324)＊
有 接種回数不明 (n=293) Unknown dose of MCV (n=293)40

接種歴不明 (n=2,899)30(n=6,628)20

無 (n=344)

Unknown vaccination history (n=2,899)
Not vaccinated (n=344)＊Measles-containing vaccine

100Antibody-negative>60
0 6 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 25 30 35 40 45 50 55 60
=
5 11

M M

0 year

24 29 34 39 44 49 54 59
血清採取時の年齢（歳）Age in years on the day of blood collection(ゼラチン粒子凝集法：ＰＡ法）(Particle agglutination assay)（感染症流行予測調査：2020年2月現在暫定値）(National Epidemiological Surveillance of Vaccine-Preventable Diseases: as of February, 2020)