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ISDS 2012 Conference Abstracts

Estimation of Influenza Incidence by Age in the 2011/12
Seasons in Japan using SASSy
Yasushi Ohkusa*1, Yoshinori Yasui1, Tamie Sugawara1, Nobuhiko Okabe2, 1, Kiyosu
Taniguchi1 and Kazunori Oishi1

1IDSC,NIID, Shinjuku, Japan; 2Kawasaki City Institute for Public Health, Kawasaki, Japan

Objective
So far, it is difficult to show the incidence rate of influenza in the

official sentinel surveillance in Japan. Hence we construct the sys-
tem which record infectious diseases at schools, kindergartens, and
nursery schools, and then can show the accurate incidence rate of in-
fluenza in children by age/grade.

Introduction
So as to develop more effective countermeasures against influenza,

timely and precise information about influenza activity at schools,
kindergartens, and nursery schools may be helpful. At the Infectious
Diseases Surveillance Center of the National Institute of Infectious
Diseases, a School Absenteeism Surveillance System (SASSy) has
been in operation since 2009. SASSy monitors the activity of vari-
cella, mumps, mycoplasma pneumonia, pharyngoconjunctival fever,
hand-foot-mouth disease, influenza, and many other infectious dis-
eases in schools. In 2010, SASSy was extended to the Nursery School
Absenteeism Surveillance System (NSASSy). These systems record
the number of absentees due to infectious diseases in each class of all
grades of schools every day. As a powerful countermeasure to the
pandemic flu of 2009, SASSy was activated in 9 prefectures, in which
included more than 6000 schools, and it is gradually being adopted in
other prefectures. As of February 2012, 18 prefectures and 4 big
cities, which together comprised 15,700 schools (about 35% of all
schools in Japan), utilized SASSy. NSASSy is used in more than 4100
nursery schools, which is about 18% of all nursery schools in Japan.
Some studies of similar systems were performed in the UK (1), Hong
Kong (2), and the USA (3,4), examined surveillance systems for mon-
itoring infectious disease incidence, but the systems to construct in
those studies do not operate nationwide like SASSy or NSASSy, and
they cannot provide influenza incidence rates in children.

Methods
All schools, kindergartens, and nursery schools in the community,

enter data of the absentees due to infectious diseases into the system
every day, thereby providing real-time data regarding infectious dis-
eases prevalent in schools, to the schools around, school boards, pub-
lic health centers, local governments, and medical professionals. It
analyzed data for the 2011/2012 season (from September 1, 2011 to
March 31, 2012) mainly, but also two seasons (2010/2011 and
2011/2012) were compared in some prefectures. In total, 12 prefec-
tures, which comprised 2,352,839 children, were participated in
2011/2012 season. In the 2010/2011 season, 1,795,766 children of 9
prefectures were analyzed.

Results
The incidence rate in the first grade of elementary schools is the

highest both in the two seasons. The highest incidence rate in this
grade distributes from 17.8% to 40.3% in 2011/2012 season, and from
11.0% to 30.7% in 2010/2011 season.

Conclusions
This study proved SASSy and NSASSy are quite useful for mon-

itoring of influenza outbreak in schools and it will be gold standard
of surveillance for school children in Japan. The present study also
showed incidence rate of influenza in children at schools, kinder-
gartens, and nursery schools, and proved the highest incidence was in
the first grade of the elementary school. This is the first finding using
such the huge number of subjects, which is more than 2 million. The
intervention targeting to the weak age/grade is necessary for effective
countermeasure and control of influenza and other infectious dis-
eases.

Keywords
Surveillance; Influenza; School Absenteeism

Acknowledgments

This paper is financial supported by Ministry Health, Labour and Wel-
fare, Japan.

References

1) Schmidt WP, Pebody R, Mangtani P: School absence data for influenza
surveillance: a pilot study in the United Kingdom, Eurosurveillance,
Volume 15, Issue 3, 21 January 2010

2) Calvin K.Y. Cheng, Benjamin J. Cowling, Eric H.Y. Lau, Lai Ming
Ho, Gabriel M. Leung, and Dennis K.M. Ip, Electronic School Ab-
senteeism Monitoring and Influenza Surveillance, Hong Kong, Emerg
Infect Dis. 2012 May

3) Buehler JW, Berkelman RL, Hartley DM, Peters CJ: Syndromic sur-
veillance and bioterrorism-related epidemics. Emerg Infect Dis. 2003;
9:1197-204.

4) Besculides M, Heffernan R, Mostashari F, Weiss D.:Evaluation of
school absenteeism data for early outbreak detection, New York City.
BMC Public Health. 2005 Oct 7;5:105

*Yasushi Ohkusa
E-mail: ohkusa@nih.go.jp

Online Journal of Public Health Informatics * ISSN 1947-2579 * http://ojphi.org * 5(1):e142, 2013