病原微生物検出情報 Vol. 35 No. 3（2014. 3） （ 251 ）ISSN 0915-5813

IASR

Vol. 35 No. 11 November 2014
Infectious Agents Surveillance Report
http://www.nih.go.jp/niid/en/iasr-e.html

Analysis of influenza virus isolates in the 2013/14 season, Japan ..... 254
Trends of influenza epidemic of the 2013/14 season according tothe pathogen surveillance, Japan...................................................... 258
Trends of the seasonal influenza epidemic according to thehospitalization surveillance in the 2013/14 season, Japan .............. 261
Epidemic of influenza virus in the 2013/14 season-Okinawa
Prefecture ........................................................................................... 262
Prevalence of the influenza antibody positives prior to the 2013/14
season, Japan-FY 2013 National Surveillance of VaccinePreventable Diseases ......................................................................... 264
Process of selection of influenza vaccine strains for the 2014/15
season, Japan ..................................................................................... 267
Antigenicity of influenza vaccine strains, which was altered throughthe virus adaptation to the egg and matching of its antigenicity
to the epidemic strains....................................................................... 269
The second wave of avian influenza A (H7N9) epidemic in themainland China ................................................................................. 271

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

Properties of the AH3 subtype influenza isolates from an outbreakin a nursing home for the elderly, August 2014-Mie Prefecture .... 272
Characteristics of subtype AH3 influenza virus isolated from thelatter half of the 2013/14 season to the beginning of the 2014/15
season (week 35-36 of 2014)-Mie Prefecture .................................. .272
A falciparum malaria case who visited a community hospital after
returning from West Africa ................................................................ 274
Enteroviruses detected from the environmental water in April toDecember in 2013 through the National Epidemiological
Surveillance of Vaccine-Preventable Diseases: Environmental
surveillance of poliovirus ................................................................... 275
Descriptive epidemiology of dengue cases in Japan-January toSeptember, 2014 ................................................................................. 276
A virus isolate in the past, which turned out to be adenovirus 57(HAdV57) -Osaka Prefecture............................................................ 278
Measles epidemic in a kindergarten, March to April, 2014
-Wakayama City................................................................................ 278<THE TOPIC OF THIS MONTH>
2013/14 influenza season, Japan

850
800
750
700
650
600
550
500
450
400
350
300
250200150
10050035
AH1pdm09
AH3
B/Victoria

No. of cases/sentinel clinic(National Epidemiological
Surveillance of Infectious
Diseases)

B/Yamagata
302030402530202010150101018 20 22 24 26 28 30 32 34 36 38 40

05

No. of cases/sentinel clinic

No. of isolated viruses

Figure 1. Weekly cases of influenza and isolation of influenza viruses from week 18 of2013 to week 40 of 2014, Japan (Infectious Agents Surveillance Report: as of October 23, 2014)22 24 26 28 30 32 34 36 38 40 42 44 46

018 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 Week

2013

2014

YearIn the 2013/14 season (from week 36/September of 2013 to week 35/August of 2014), influenza A(H1N1)pdm09 (AH1pdm09)
became the main strain for the first time in past 3 seasons; other epidemic strains were influenza virus type B followed by thesubtype AH3. The number of patients reached the peak in January as usual.
Incidence of Influenza patients: Under the National Epidemiological Surveillance of Infectious Diseases (NESID), 5,000
influenza sentinels (3,000 pediatric and 2,000 internal medicine clinics) report influenza cases at weekly basis (http://www.nih.
go.jp/niid/images/iasr/34/405/de4051.pdf). The number of patients/week/sentinel (epidemic index) exceeded 1.0 in the nationallevel (a sign of start of the epidemic season) in week 51 of 2013 and the level was maintained for 21 weeks till week 19 of 2014(http://www.nih.go.jp/niid/en/10/2096-weeklygraph/2572-trend-week-e.html). The epidemic reached its peak in week 5 of 2014 with
the incidence of 34.4 cases/sentinel (Fig. 1), whose level was the same as that of the previous season (36.4 per sentinel in week 4 of2013). The total number of patients per sentinel for the whole season was 301.0 (239.0 in 2012/13 season).
In prefecture levels, the epidemic index exceeded 10.0 first in Okinawa in the 1st week of 2014. The number of prefectures withthe epidemic index exceeding 10.0 increased to 30 in week 3 of 2014 and to 47 all prefectures in week 5, and then the influenza
epidemic expanded nationwide. In 2013/14 season, Okinawa Prefecture didn’t experience the summer season influenza that occurred
every year since 2005 (see p. 262 of this issue).
The total number of influenza patients visiting medical institutions, which was estimated from sentinel reports, was about15,720,000 from week 36 of 2013 to week 21 of 2014 (September 2, 2013-May 25, 2014).
The hospitalization surveillance started in September 2011 for estimating number of severe influenza cases. According to its
report, total 9,905 patients were hospitalized in about 500 “designated hospital sentinels with ≥300 beds” in this season. The numberof hospitalized patients was 5% less than in the previous season (10,373 in 2012/13) (see p. 261 of this issue).
Isolation/detection of influenza virus: In 2013/14 season, the prefectural and municipal public health institutes (PHIs)
reported total 8,230 isolation/detections (6,345 isolations and 1,885 detections without virus isolation) (Table 1 in p. 253 of thisissue). Among them, 6,738 were reported from influenza sentinels and 1,492 from elsewhere (Table 2 in p. 253, see p. 258 of this issue).
Influenza virus isolated/detected in the 2013/14 season consisted of AH1pdm09 (43%), subtype AH3 (21%) and type B (36%).
AH1pdm09 became dominant for the first time since 2010/11 season. Among type B viruses, ratio of Yamagata lineage to Victorialineage was 7:3 (Table 1 in p. 253). The subtype AH3 reached the peak in week 4 of 2014, and then declined. Type B exceeded type
A in week 10 of 2014 (Fig. 1; Fig. 2 in p. 253). The peak age was 5-9 years both for AH1pdm09 and type B Yamagata lineage (Fig. 3and see p. 258 of this issue).
Antigenic characteristics of the 2013/14 season isolates and their drug resistance (see p. 254 of this issue): National
Institute of Infectious Diseases conducted detailed antigen analysis of isolates from Japan and other Asian countries. All of the 255AH1pdm09 isolates, except one antigen variant, were antigenically similar to the vaccine strain A/California/7/2009. All of the 2441′（251′）（Continued on page 252′）IASR Vol. 35 No. 11（Nov. 2014） 2′（252′）（ 252 ） 病原微生物検出情報 Vol. 35 No. 3（2014. 3）（THE TOPIC OF THIS MONTH-Continued）

Figure 3. Age distribution of cases with isolation of influenza virus AH1pdm09, AH3,
B/Victoria and B/Yamagata in 2013/14 season, Japan(Infectious Agents Surveillance Report: as of October 14, 2014)
01020304050607080100 %90No. of cases*1519404950 60
59 69B/Victoria

B/Yamagata

2,814_ 1,191
70 <-AH33039-202943-

2-

1-

0-

AH1pdm09621

5678910Age group1112 13 14

1,626*Excluding age-unknown cases

subtype AH3 isolates were antigenically similar to the vaccine strain A/Texas/50/2012. All of the 163 Yamagata lineage isolates wereall antigenically similar to vaccine strain B/Massachusetts/02/2012; among them 28% of the isolates belonged to the clade 2 genetictype (same as 2013/14 season vaccine strain), and 72% to the clade 3 genetic type (represented by B/Wisconsin/1/2010, a 2012/13
season vaccine strain). All of the 104 Victoria lineage isolate were antigenically similar to the vaccine strain B/Brisbane/60/2008.
Among 2,524 AH1pdm09 isolates in Japan, 105 isolates (4.2%) had the H275Y mutation, a marker of the oseltamivir/peramivirresistance. Sapporo City in Hokkaido experienced a local epidemic of the H275Y mutant from November 2013 to February 2014;as a consequence, the mutant occupied 28% of all the isolates in Hokkaido. So far tested, subtype AH3 and type B isolated in Japan
were all sensitive to oseltamivir, zanamivir, peramivir, and laninamivir.
Immunological status of Japanese population (see p. 264 of this issue): According to the sero-surveillance conductedunder the National Epidemiological Surveillance of Vaccine-Preventable Diseases (FY2013), among 6,571 sera collected before the2013/14 season (from July to September in 2013), the HI antibody positives (≥1:40) to A/California/7/2009[A(H1N1)pdm09] were≥70% in the population in their teens and early twenties, and 20-30% among population younger than 4 years or older than 55years. The population HI antibody positive to A/Texas/50/2012 [A(H3N2)] was around 40-50% or more in all the age groups exceptage group <4 years and 60-64 years whose antibody positive rate was relatively low (~30%). Antibody positives to B/Massachusetts/
02/2012 (B Yamagata lineage) occupied >50% among population aged 15-29 years (highest among 20-24 year olds) and ~10% among
the population younger than 4 years. The percentage of the antibody positives to B/Brisbane/60/2008 (B Victoria lineage) was thehighest (~50%) among population aged 35-44 years, and ~20% among <4 year and 60-64 year aged groups.
Influenza vaccine: The quantity of trivalent vaccines produced for 2013/14 season was 33,880,000 vials (1ml/vial), of which
estimated 25,810,000 vials were used.
The vaccine strain selected for 2014/15 season for the AH1 subtype was A/California/7/2009pdm09 (X-179A) which was the same
as for 2010/11-2013/14 seasons, whereas the vaccine strain for AH3 was changed to A/New York/39/2012 (X-233A) strain. The vaccine
strain for type B was B/Massachusetts/2/2012 (BX-51B) (Yamagata lineage) as in 2013/14 season (see pp. 267 & 269 of this issue).
Avian influenza A(H7N9): In China, influenza virus A(H7N9) broke out late in March 2013. So far, total 454 confirmed cases
including 171 deaths have been reported. The epidemic consisted of two waves, the second wave (since October 2013) being larger
in scale than the first (before October 2013). The number of patients in the second wave was 318 and that of deaths 127 (see p. 271of this issue).
The avian influenza H7N9 was classified as “designated infectious disease” on 26 April, 2013 in Japan. Its laboratory diagnosis
is now possible in 74 PHIs and 16 quarantine laboratories in Japan. All the laboratories have already received the H7N9 detection
manual and the test kits (reagents for PCR tests, primers, probes, and a positive reference, etc.).
Avian influenza A(H5N1): In 2014, total 13 cases including 6 deaths (9 cases including 4 deaths in Cambodia; 2 cases andzero deaths in China, and 2 cases including 2 deaths in Vietnam) were reported (as of 17 October) (http://www.wpro.who.int/emerging_diseases/AvianInfluenza/en/).
Avian influenza in Japan: In April 2014, there was an outbreak of the highly pathogenic avian influenza in a meat poultry
farm in Kumamoto Prefecture. On the 22nd day after the completion of the preventive measures, the setting of the movement
restriction area has been released. The genotype of the virus was identical to that H5N8 subtype isolated in the Republic of Korea
suggesting its Korean origin.
Act on special measures against the new type influenza: The act was issued on 11 May 2012 and enforced on 13 April
2013 with the objectives of protecting life and health of Japanese citizens and minimizing the adverse effects on the daily life andeconomy. The Japanese government produced a government action plan and all the prefectures in Japan completed prefecture level
action plan in June 2013.
Additional comments: Trends of influenza outbreaks should be monitored continuously by sentinel surveillance, school outbreak surveillance, hospitalization surveillance and other possibilities. The virus isolation should be conducted throughout theyear and the antigenic and genetic changes of the epidemic strains should be monitored so as to secure vaccine candidate strains.
Monitoring of the resistance to anti-influenza drugs among isolates and the antibody level of Japanese population should be continued
for risk management in future.
Flash reports on the isolation and detection of influenza viruses in 2013/14 season are found in see p. 272 of this issue andhttp://www.nih.go.jp/niid/en/iasr-inf-e.html.
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 Law Concerning the Prevention of Infectious Diseases and Medical Care forPatients of Infections, and 2) other data covering various aspects of infectious diseases. The prefectural and municipal health centers and publichealth institutes (PHIs), the Department of Food Safety, the Ministry of Health, Labour and Welfare, and quarantine stations, have provided theabove 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. 35 No.11（2014. 11） 3 （253）（特集つづき）表1. インフルエンザウイルス分離・検出報告数, 2010/11〜2013/14シーズン
Table 1. Isolation/detection of influenza viruses during 2010/11-2013/14 seasons*ᆺ*䝅䞊䝈䞁 䚷Season
2010/112011/122012/132013/14
A H1pdm09
3,819 ( 2,438)
11 (4)109 (54)
2,841 (654)
A H1
A H3
2,339 ( 1,523)
3,709 ( 1,434)
3,667 ( 1,379)
1,199 (534)
A NT
- (2)
- (14)- (15)- (4)B/Victoria
1,450 (3)1,088 (14)357 (28)627 (116)B/Yamagata33
547 (8)805 (31)
1,637 (295)
B NT
49 (313)82 (304)49 (195)
20 (273)
C- (12)25 (36)- (2)21 (9)
ྜィ Total
7,690 ( 4,291)
5,462 ( 1,814)
4,987 ( 1,704)
6,345 ( 1,885)
A NT: Aளᆺᮍྠᐃ㻘㻌B NT: B⣔⤫ᮍྠᐃA NT: A not subtyped, B NT: B lineage not determined*ྛ䝅䞊䝈䞁㻔ᙜᖺ9᭶䡚⩣ᖺ8᭶㻕䛻᥇ྲྀ䛥䜜䛯᳨య䛛䜙ྛᆅ᪉⾨⏕◊✲ᡤ䛷ศ㞳䛥䜜䛯䜴䜲䝹䝇ሗ࿌ᩘ, 䠉ሗ࿌䛺䛧㻘㻌䠄 䠅ෆ䛿䜴䜲䝹䝇䛿ศ㞳䛥䜜䛶䛔䛺䛔䛜㻘㻌㑇ఏᏊ᳨ฟ䜎䛯䛿ᢠཎ᳨ฟ䛻䜘䜛ሗ࿌ᩘ䜢ูᥖ䠄⑓ཎᚤ⏕≀᳨ฟ᝟ሗ 㻦 2014ᖺ10᭶14᪥⌧ᅾሗ࿌ᩘ䠅*Sampling season during September through August in the following year.
( ): Gene or antigen detection, not included in the total[Infectious Agents Surveillance Report: as of October 14, 2014 from prefectural andmunicipal public health institutes (PHIs)]

Type

表2. インフルエンザウイルス分離・検出報告数,
2013/14シーズン
Table 2. Isolation/detection of influenza viruses,
2013/14 season
ᆺ TypeTotal (A+B)(A)(B)
A H1pdm09
3,495
2,792703
A H1A H3
1,733
1,424309
A NT
4
13
B/Victoria
743
639
104
B/Yamagata
1,932
1,637295
B NT293
22766
C181230ྜィ Total
8,230
6,738
1,492(A) 䜲䞁䝣䝹䜶䞁䝄ᐃⅬ䠄ᑠඣ⛉+ෆ⛉䠅Reports frominfluenza sentinels (pediatric & internal medicineclinics)(B) 䜲䞁䝣䝹䜶䞁䝄ᐃⅬ௨እ䠄ᇶᖿᐃⅬ+䛭䛾௚䠅
Other reports from hospital sentinels & clinics
A NT: Aளᆺᮍྠᐃ㻘㻌B NT: B⣔⤫ᮍྠᐃA NT: A not subtyped, B NT: B lineage not determined2013ᖺ9᭶䡚2014ᖺ8᭶䛻᥇ྲྀ䛥䜜䛯᳨య䜘䜚ྛᆅ᪉⾨⏕◊✲ᡤ䛷ศ㞳䞉᳨ฟ䛥䜜䛯䜴䜲䝹䝇ሗ࿌ᩘ㻘㻌䠉㻦㻌ሗ࿌䛺䛧䠄⑓ཎᚤ⏕≀᳨ฟ᝟ሗ 㻦 2014ᖺ10᭶14᪥⌧ᅾሗ࿌ᩘ䠅
Detections from samples collected during September
2013 through August 2014.
(Infectious Agents Surveillance Report: as of October 14,
2014 from PHIs)

図2. 都道府県別インフルエンザウイルス分離報告状況, 2013/14シーズン（病原微生物検出情報 : 2014年10月14日現在報告数）

Figure 2. Isolation of influenza viruses by prefecture in 2013/14 season(Infectious Agents Surveillance Report: As of October 14, 2014 from PHIs)
Weeks 43-47(Oct.21-Nov.24)

AH1pdm09
Reports of isolation
01
2-5
6-10
11-AH3

Reports of isolation
0
1
2-5
6-10
11-

B/Victoria
Reports of isolation
0
1
2-5
6-10
11-

B/Yamagata
Reports of isolation
01
2-5
6-10
11-

Weeks 48-52(Nov.25-Dec.29)

Weeks 1-5
(Dec.30-Feb.2)

Weeks 6-10
(Feb.3-Mar.9)

Weeks 11-15(Mar.10-Apr.13)

Weeks 16-20(Apr.14-May18)